7 Describing Schema Metadata
This chapter discusses the use of the OCIDescribeAny()
function to obtain information about schema elements.
This chapter contains these topics:
See Also:
7.1 About Using OCIDescribeAny()
Performs an explicit describe of schema objects and their subschema objects.
The OCIDescribeAny()
function enables you to perform an explicit describe of the following schema objects and their subschema objects:
-
Tables and views
-
Synonyms
-
Procedures
-
Functions
-
Packages
-
Sequences
-
Collections
-
Types
-
Schemas
-
Databases
Information about other schema elements (function arguments, columns, type attributes, and type methods) is available through a describe of one of the preceding schema objects or an explicit describe of the subschema object.
When an application describes a table, it can then retrieve information about that table's columns. Additionally, OCIDescribeAny()
can directly describe subschema objects such as columns of a table, packages of a function, or fields of a type if given the name of the subschema object.
The OCIDescribeAny()
call requires a describe handle as one of its arguments. The describe handle must be previously allocated with a call to OCIHandleAlloc()
.
The information returned by OCIDescribeAny()
is organized hierarchically like a tree, as shown in Figure 7-1.
Figure 7-1 OCIDescribeAny() Table Description
Description of "Figure 7-1 OCIDescribeAny() Table Description"
The describe handle returned by the OCIDescribeAny()
call has an attribute, OCI_ATTR_PARAM
, that points to such a description tree. Each node of the tree has attributes associated with that node, as well as attributes that are like recursive describe handles and point to subtrees containing further information. If all the attributes are homogenous, as with elements of a column list, they are called parameters. The attributes associated with any node are returned by OCIAttrGet()
, and the parameters are returned by OCIParamGet()
.
A call to OCIAttrGet()
on the describe handle for the table returns a handle to the column-list information. An application can then use OCIParamGet()
to retrieve the handle to the column description of a particular column in the column list. The handle to the column descriptor can be passed to OCIAttrGet()
to get further information about the column, such as the name and data type.
After a SQL statement is executed, information about the select list is available as an attribute of the statement handle. No explicit describe call is needed. To retrieve information about select-list items from the statement handle, the application must call OCIParamGet()
once for each position in the select list to allocate a parameter descriptor for that position.
Note:
No subsequent OCIAttrGet()
or OCIParamGet()
call requires extra round-trips, as the entire description is cached on the client side by OCIDescribeAny()
.
7.1.1 Limitations on OCIDescribeAny()
The OCIDescribeAny()
call limits information returned to the basic information and stops expanding a node if it amounts to another describe operation.
For example, if a table column is of an object type, then OCI does not return a subtree describing the type, because this information can be obtained by another describe call.
The table name is not returned by OCIDescribeAny()
or the implicit use of OCIStmtExecute()
. Sometimes a column is not associated with a table. In most cases, the table is already known.
7.1.2 Notes on Types and Attributes
What to be aware of when performing describe operations.
7.1.2.1 Data Type Codes
The OCI_ATTR_TYPECODE
attribute returns typecodes that represent the types supplied by the user when a new type is created using the CREATE TYPE
statement.
These typecodes are of the enumerated type OCITypeCode
, and are represented by OCI_TYPECODE
constants. Internal PL/SQL type (boolean) is supported.
The OCI_ATTR_DATA_TYPE
attribute returns typecodes that represent the data types stored in database columns. These are similar to the describe values returned by previous versions of Oracle Database. These values are represented by SQLT constants (ub2
values). Boolean types return SQLT_BOL
.
See Also:
-
External Data Types for more information about
SQLT_BOL
-
Typecodes for more information about typecodes, such as the
OCI_TYPECODE
values returned in theOCI_ATTR_TYPECODE
attribute and the SQLT typecodes returned in theOCI_ATTR_DATA_TYPE
attribute
7.1.2.2 About Describing Types
To describe type objects, it is necessary to initialize the OCI process in object mode.
This is shown in Example 7-1.
Example 7-1 Initializing the OCI Process in Object Mode
/* Initialize the OCI Process */ if (OCIEnvCreate((OCIEnv **) &envhp, (ub4) OCI_OBJECT, (voivoid *) 0, (void * (*)(void *,size_t)) 0, (void * (*)(void *, void *, size_t)) 0, (void (*)(void *, void *)) 0, (size_t) 0, (void **) 0)) { printf("FAILED: OCIEnvCreate()\n"); return OCI_ERROR; }
See Also:
7.1.2.3 Implicit and Explicit Describe Operations
The column attribute OCI_ATTR_PRECISION
can be returned using an implicit describe with OCIStmtExecute()
and an explicit describe with OCIDescribeAny()
.
When you use an implicit describe, set the precision to sb2
. When you use an explicit describe, set the precision to ub1
for a placeholder. This is necessary to match the data type of precision in the dictionary.
See Also:
7.1.2.4 OCI_ATTR_LIST_ARGUMENTS Attribute
The OCI_ATTR_LIST_ARGUMENTS
attribute for type methods represents second-level arguments for the method.
For example, consider the following record my_type
and the procedure my_proc
that takes an argument of type my_type:
my_type record(a number, b char) my_proc (my_input my_type)
In this example, the OCI_ATTR_LIST_ARGUMENTS
attribute would apply to arguments a
and b
of the my_type
record.
7.2 Parameter Attributes
This section describes the attributes and handles that belong to different parameters.
A parameter is returned by OCIParamGet()
. Parameters can describe different types of objects or information, and have attributes depending on the type of description they contain, or type-specific attributes.
The OCIDescribeAny()
call does support more than two name components (for example, schema.type.attr1.attr2.method1
). With more than one component, the first component is interpreted as the schema name (unless some other flag is set). There is a flag to specify that the object must be looked up under PUBLIC, that is, describe "a", where "a" can be either in the current schema or a public synonym.
If you do not know what the object type is, specify OCI_PTYPE_UNK
. Otherwise, an error is returned if the actual object type does not match the specified type.
Table 7-1 lists the attributes of all parameters.
Table 7-1 Attributes of All Parameters
Attribute | Description | Attribute Data Type |
---|---|---|
OCI_ATTR_LIST_ANNOTATIONS |
Retrieves annotations from tables, views, and columns | OCI_PTYPE_LIST |
OCI_ATTR_NUM_ANNOTATIONS |
Retrieves the number of annotations for an object | ub4 |
OCI_ATTR_ANNOTATION_KEY |
Retrieves the text value for an annotation | text |
OCI_ATTR_ANNOTATION_VALUE |
Retrieves the value in the key-value pair of an annotation. Used
along with OCI_ATTR_ANNOTATION_KEY to get the complete
annotation.
|
text |
OCI_ATTR_HAS_JSON_SCHEMA |
Indicates if a column has JSON schema constraint | ub1 |
|
Object or schema ID |
ub4 |
|
Database name or object name in a schema |
OraText * |
|
Schema name where the object is located |
OraText * |
|
Type of information described by the parameter. Possible values:
|
ub1 |
|
The time stamp of the object on which the description is based in Oracle date format |
ub1 * |
OCI_ATTR_DOMAIN_NAME |
Accesses the domain name | OraText * |
OCI_ATTR_DOMAIN_SCHEMA |
Accesses the domain schema | OraText * |
See Also:
7.2.1 Table or View Parameters
Lists and describes the type-specific attributes for parameters for a table or view.
Table 7-2 lists the type-specific attributes for parameters for a table or view (type OCI_PTYPE_TABLE
or OCI_PTYPE_VIEW
).
Table 7-2 Attributes of Tables or Views
Table 7-3 lists additional attributes that belong to tables.
Table 7-3 Attributes Specific to Tables
Attribute | Description | Attribute Data Type |
---|---|---|
Data block address of the segment header |
ub4 |
|
Tablespace that the table resides in |
word |
|
Indicates that the table is clustered |
ub1 |
|
Indicates that the table is partitioned |
ub1 |
|
Indicates that the table is index-only |
ub1 |
7.2.2 Procedure, Function, and Subprogram Attributes
Lists and describes the type-specific attributes when a parameter is for a procedure or function.
Table 7-4 lists the type-specific attributes when a parameter is for a procedure or function (type OCI_PTYPE_PROC
or OCI_PTYPE_FUNC
).
Table 7-4 Attributes of Procedures or Functions
Attribute | Description | Attribute Data Type |
---|---|---|
|
Argument list. See List Attributes. |
void * |
|
Indicates that the procedure or function has invoker's rights |
ub1 |
Table 7-5 lists the attributes that are defined only for package subprograms.
Table 7-5 Attributes Specific to Package Subprograms
Attribute | Description | Attribute Data Type |
---|---|---|
|
Name of the procedure or function |
OraText * |
|
Overloading ID number (relevant in case the procedure or function is part of a package and is overloaded). Values returned may be different from direct query of a PL/SQL function or procedure. |
ub2 |
7.2.3 Package Attributes
Lists and describes the attributes when a parameter is for a package.
Table 7-6 lists the attributes when a parameter is for a package (type OCI_PTYPE_PKG
).
Table 7-6 Attributes of Packages
Attribute | Description | Attribute Data Type |
---|---|---|
|
Get a list of all types in an |
void * |
|
Subprogram list. See List Attributes. |
void * |
|
Indicates that the package has invoker's rights? |
ub1 |
7.2.4 Type Attributes
Lists and describes the attributes when a parameter is for a type.
Table 7-7 lists the attributes when a parameter is for a type (type OCI_PTYPE_TYPE
). These attributes are only valid if the application initialized the OCI process in OCI_OBJECT
mode in a call to OCIEnvCreate()
.
Table 7-7 Attributes of Types
Attribute | Description | Attribute Data Type |
---|---|---|
|
Returns the in-memory |
OCIRef * |
|
Typecode. See Data Type Codes. Currently can be only |
OCITypeCode |
|
Typecode of collection if type is collection; invalid otherwise. See Data Type Codes. Currently can be only |
OCITypeCode |
|
Indicates that this is an incomplete type |
ub1 |
|
Indicates that this is a system type |
ub1 |
|
Indicates that this is a predefined type |
ub1 |
|
Indicates that this is a transient type |
ub1 |
|
Indicates that this is a system-generated type |
ub1 |
|
This type contains a nested table attribute. |
ub1 |
|
This type contains a LOB attribute. |
ub1 |
|
This type contains a |
ub1 |
|
Handle to collection element. See Collection Attributes. |
void * |
|
Number of type attributes |
ub2 |
|
List of type attributes. See List Attributes. |
void * |
|
Number of type methods |
ub2 |
|
List of type methods. See List Attributes. |
void * |
|
Map method of type. See Type Method Attributes. |
void * |
|
Order method of type. See Type Method Attributes. |
void * |
|
Indicates that the type has invoker's rights |
ub1 |
|
A pointer to a string that is the type attribute name |
OraText * |
|
A string with the package name if the attribute is a package type. |
OraText * |
|
A string with the schema name where the type has been created |
OraText * |
|
Indicates that this is a final type |
ub1 |
|
Indicates that this is an instantiable type |
ub1 |
|
Indicates that this is a subtype |
ub1 |
|
Name of the schema that contains the supertype |
OraText * |
|
Name of the supertype |
OraText * |
See Also:
7.2.5 Type Attribute Attributes
Lists and describes the attributes when a parameter is for an attribute of a type.
Table 7-8 lists the attributes when a parameter is for an attribute of a type (type OCI_PTYPE_TYPE_ATTR
).
Table 7-8 Attributes of Type Attributes
Attribute | Description | Attribute Data Type |
---|---|---|
|
The maximum size of the type attribute. This length is returned in bytes and not characters for strings and raws. It returns 22 for |
ub2 |
|
Typecode. See Data Type Codes. |
OCITypeCode |
|
The data type of the type attribute. See Data Type Codes. |
ub2 |
|
A pointer to a string that is the type attribute name |
OraText * |
|
The precision of numeric type attributes. If the precision is nonzero and scale is -127, then it is a |
ub1for explicit describe sb2for implicit describe |
|
The scale of numeric type attributes. If the precision is nonzero and scale is -127, then it is a |
sb1 |
|
A string that is the package name of a type if it is a package type. |
OraText * |
|
A string that is the type name. The returned value contains the type name if the data type is |
OraText * |
|
A string with the schema name under which the type has been created |
OraText * |
|
Returns the in-memory |
OCIRef * |
|
The character set ID, if the type attribute is of a string or character type |
ub2 |
|
The character set form, if the type attribute is of a string or character type |
ub1 |
|
The fractional seconds precision of a datetime or interval |
ub1 |
|
The leading field precision of an interval |
ub1 |
7.2.6 Type Method Attributes
Lists and dsescribes the attributes when a parameter is for a method of a type.
Table 7-9 lists the attributes when a parameter is for a method of a type (type OCI_PTYPE_TYPE_METHOD
).
Table 7-9 Attributes of Type Methods
Attribute | Description | Attribute Data Type |
---|---|---|
|
Name of method (procedure or function) |
OraText * |
|
Encapsulation level of the method (either |
OCITypeEncap |
|
Argument list. See OCI_ATTR_LIST_ARGUMENTS Attribute, and List Attributes. |
void * |
|
Indicates that method is a constructor |
ub1 |
|
Indicates that method is a destructor |
ub1 |
|
Indicates that method is an operator |
ub1 |
|
Indicates that method is selfish |
ub1 |
|
Indicates that method is a map method |
ub1 |
|
Indicates that method is an order method |
ub1 |
|
Indicates that "Read No Data State" is set for method |
ub1 |
|
Indicates that "Read No Process State" is set for method |
ub1 |
|
Indicates that "Write No Data State" is set for method |
ub1 |
|
Indicates that "Write No Process State" is set for method |
ub1 |
|
Indicates that this is a final method |
ub1 |
|
Indicates that this is an instantiable method |
ub1 |
|
Indicates that this is an overriding method |
ub1 |
7.2.7 Collection Attributes
Lists and describes the attributes when a parameter is for a collection type.
Table 7-10 lists the attributes when a parameter is for a collection type (type OCI_PTYPE_COLL
).
Table 7-10 Attributes of Collection Types
Attribute | Description | Attribute Data Type |
---|---|---|
|
The maximum size of the type attribute. This length is returned in bytes and not characters for strings and raws. It returns 22 for |
ub2 |
|
Typecode. See Data Type Codes. |
OCITypeCode |
|
The data type of the type attribute. See Data Type Codes. |
ub2 |
|
The number of elements in an array. It is only valid for collections that are arrays. |
ub4 |
|
A pointer to a string that is the type attribute name |
OraText * |
|
The precision of numeric type attributes. If the precision is nonzero and scale is -127, then it is a |
ub1 for explicit describe sb2 for implicit describe |
|
The scale of numeric type attributes. If the precision is nonzero and scale is -127, then it is a |
sb1 |
|
A string that is the package name of a type if it is a package type. |
OraText * |
|
A string that is the type name. The returned value contains the type name if the data type is |
OraText * |
|
A string with the schema name under which the type has been created |
OraText * |
|
Returns the in-memory |
OCIRef * |
|
The character set ID, if the type attribute is of a string or character type |
ub2 |
|
The character set form, if the type attribute is of a string or character type |
ub1 |
7.2.8 Synonym Attributes
Lists and describes the attributes when a parameter is for a synonym.
Table 7-11 lists the attributes when a parameter is for a synonym (type OCI_PTYPE_SYN
).
Table 7-11 Attributes of Synonyms
Attribute | Description | Attribute Data Type |
---|---|---|
|
Object ID |
ub4 |
|
A string containing the schema name of the synonym translation |
OraText * |
|
A |
OraText * |
|
A |
OraText * |
7.2.9 Sequence Attributes
Lists and describes the attributes when a parameter is for a sequence.
Table 7-12 lists the attributes when a parameter is for a sequence (type OCI_PTYPE_SEQ
).
Table 7-12 Attributes of Sequences
Attribute | Description | Attribute Data Type |
---|---|---|
|
Object ID |
ub4 |
|
Minimum value (in Oracle |
ub1 |
|
Maximum value (in Oracle |
ub1 |
|
Increment (in Oracle |
ub1 |
|
Number of sequence numbers cached; zero if the sequence is not a cached sequence (in Oracle |
ub1 |
|
Whether the sequence is ordered |
ub1 |
|
High-water mark (in |
ub1 |
See Also:
7.2.10 Column Attributes
Lists and describes the attributes when a parameter is for a column of a table or view.
Note:
For BINARY_FLOAT
and BINARY_DOUBLE
:
If OCIDescribeAny()
is used to retrieve the column data type (OCI_ATTR_DATA_TYPE
) for BINARY_FLOAT
or BINARY_DOUBLE
columns in a table, it returns the internal data type code.
The SQLT codes corresponding to the internal data type codes for BINARY_FLOAT
and BINARY_DOUBLE
are SQLT_IBFLOAT
and SQLT_IBDOUBLE
.
The following table lists the attributes when a parameter is for a column of a table or view (type OCI_PTYPE_COL
).
Table 7-13 Attributes of Columns of Tables or Views
Attribute | Description | Attribute Data Type |
---|---|---|
|
Returns the type of length semantics of the column. Zero (0) means byte-length semantics and 1 means character-length semantics. See Character-Length Semantics Support in Describe Operations. |
ub1 |
|
Returns the column character length that is the number of characters allowed in the column. It is the counterpart of |
ub2 |
|
Returns the derived collation ID of the column. The Note: You can use the SQL built-in functions See Also:
|
ub4 * |
|
Returns describe data regarding certain column properties. The following are the flags available in
The following is a sample usage: OCIAttrGet((dvoid*) mypard, (ub4) OCI_DTYPE_PARAM, (dvoid*) &col_prop, (ub4 *) 0,(ub4) OCI_ATTR_COL_PROPERTIES, (OCIError *) errhp )); if(col_prop & OCI_ATTR_COL_PROPERTY_IS_IDENTITY) printf("Identity Column \n"); if(col_prop & OCI_ATTR_COL_PROPERTY_IS_GEN_ALWAYS) printf("Column is always generated\n"); if(col_prop & OCI_ATTR_COL_PROPERTY_IS_GEN_BY_DEF_ON_NULL) printf("Column is generated by default on NULL\n"); if(col_prop & OCI_ATTR_COL_PROPERTY_IS_LPART) printf("Column is an implicitly generated logical partitioning column for container_map enabled objects\n"); if(col_prop & OCI_ATTR_COL_PROPERTY_IS_CONID) printf("Column is a CON_ID column implicitly generated by CONTAINERS() or is an ORIGIN_CON_ID column implicitly generated for Extended Data Link\n"); See Oracle Database SQL Language Reference for more information about the SQL syntax to specify these properties in an identity clause for a column definition in the |
ub8 |
|
Returns whether a column is invisible or not. A value of |
ub1 |
|
The maximum size of the column. This length is returned in bytes and not characters for strings and raws. It returns 22 for |
ub2 |
|
The data type of the column. See Data Type Codes. |
ub2 |
|
A pointer to a string that is the column name |
OraText * |
|
The precision of numeric columns. If the precision is nonzero and scale is -127, then it is a |
ub1 for explicit describe sb2 for implicit describe |
|
The scale of numeric columns. If the precision is nonzero and scale is -127, then it is a |
sb1 |
|
Returns 0 if null values are not permitted for the column. Does not return a correct value for a |
ub1 |
|
Returns a string that is the type name. The returned value contains the type name if the data type is |
OraText * |
|
Returns a string with the schema name under which the type has been created |
OraText * |
|
The |
OCIRef * |
|
The character set ID, if the column is of a string or character type |
ub2 |
|
The character set form, if the column is of a string or character type |
ub1 |
Table 7-14 describes predefined constants for a number of commonly used collation IDs, which can be returned for the attribute OCI_ATTR_COLLATION_ID
. The constants are listed with their values (in parenthesis) and the SQL names of the corresponding collations.
Table 7-14 Predefined Collation IDs, Their ub4
Values (in parenthesis), and Their SQL Names
Collation ID (Value) | SQL Name |
---|---|
OCI_COLLATION_NONE (0) | Undefined collation; no collation has been specified. |
OCI_COLLATION_NLS_COMP (16382) | USING_NLS_COMP |
OCI_COLLATION_NLS_SORT (16381) | USING_NLS_SORT |
OCI_COLLATION_NLS_SORT_CI (16380) | USING_NLS_SORT_CI |
OCI_COLLATION_NLS_SORT_AI (16379) | USING_NLS_SORT_AI |
OCI_COLLATION_NLS_SORT_CS (16378) | USING_NLS_SORT_CS |
OCI_COLLATION_BINARY (16383) | BINARY |
OCI_COLLATION_BINARY_CI (147455) | BINARY_CI |
OCI_COLLATION_BINARY_AI (81919) | BINARY_AI |
See Also:
7.2.11 Argument and Result Attributes
Lists and describes the attributes when a parameter is for an argument of a procedure or function.
Table 7-15 lists the attributes when a parameter is for an argument of a procedure or function (type OCI_PTYPE_ARG
), for a type method argument (type OCI_PTYPE_TYPE_ARG
), or for method results (type OCI_PTYPE_TYPE_RESULT
).
Table 7-15 Attributes of Arguments and Results
Attribute | Description | Attribute Data Type |
---|---|---|
|
Returns a pointer to a string that is the argument name |
OraText * |
|
The position of the argument in the argument list. Always returns zero. |
ub2 |
|
Typecode. See Data Type Codes. |
OCITypeCode |
|
The data type of the argument. See Data Type Codes. |
ub2 |
|
The size of the data type of the argument. This length is returned in bytes and not characters for strings and raws. It returns 22 for |
ub2 |
|
The precision of numeric arguments. If the precision is nonzero and scale is -127, then it is a |
|
|
The scale of numeric arguments. If the precision is nonzero and scale is -127, then it is a |
|
|
The data type levels. This attribute always returns zero. |
ub2 |
|
Indicates whether an argument has a default |
ub1 |
|
The list of arguments at the next level (when the argument is of a record or table type) |
void * |
|
Indicates the argument mode: 0 is IN ( 1 is OUT ( 2 is IN/OUT ( |
OCITypeParamMode |
|
Returns a radix (if number type) |
ub1 |
|
Returns 0 if null values are not permitted for the column |
ub1 |
|
Returns a string that is the type name or the package name for package local types. The returned value contains the type name if the data type is |
OraText * |
|
For |
OraText * |
|
For |
OraText * |
|
For |
OraText * |
|
Returns the |
OCIRef * |
|
Returns the character set ID if the argument is of a string or character type |
ub2 |
|
Returns the character set form if the argument is of a string or character type |
ub1 |
7.2.12 List Attributes
Lists and describes the attributes when the parameter is for a list of columns, arguments, and subprograms, or fields of a package record type.
When a parameter is for a list of columns, arguments, and subprograms, or fields of a package record type (type OCI_PTYPE_LIST
), it has the type-specific attributes and handles (parameters) shown in Table 7-16.
The list has an OCI_ATTR_LTYPE
attribute that designates the list type. Table 7-16 lists the possible values and their lower bounds when traversing the list.
Table 7-16 List Attributes
List Attribute | Description | Lower Bound |
---|---|---|
|
Column list |
1 |
|
Procedure argument list |
1 |
|
Function argument list |
0 |
|
Subprogram list |
0 |
|
Type attribute list |
1 |
|
Type method list |
1 |
|
Type method without result argument list |
0 |
|
Type method without result argument list |
1 |
|
Object list within a schema |
0 |
|
Schema list within a database |
0 |
The list has an OCI_ATTR_NUM_PARAMS
attribute, which tells the number of elements in the list.
Each list has LowerBound
... OCI_ATTR_NUM_PARAMS
parameters. LowerBound
is the value in the Lower Bound column of Table 7-16. For a function argument list, position 0 has a parameter for the return value (type OCI_PTYPE_ARG
).
7.2.13 Schema Attributes
Lists and describes the attributes when a parameter is for a schema type.
Table 7-17 lists the attributes when a parameter is for a schema type (type OCI_PTYPE_SCHEMA
).
Table 7-17 Attributes Specific to Schemas
Attribute | Description | Attribute Data Type |
---|---|---|
|
List of objects in the schema |
OCIParam * |
7.2.14 Database Attributes
Lists and describes the attributes when a parameter is for a database type.
Table 7-18 lists the attributes when a parameter is for a database type (type OCI_PTYPE_DATABASE
).
Table 7-18 Attributes Specific to Databases
Attribute | Description | Attribute Data Type |
---|---|---|
|
Database version |
OraText * |
|
Database character set ID from the server handle |
ub2 |
|
Database national character set ID from the server handle |
ub2 |
|
List of schemas (type |
ub1 |
|
Maximum length of a procedure name |
ub4 |
|
Maximum length of a column name |
ub4 |
|
How a
|
ub1 |
|
Maximum length of a catalog (database) name |
ub1 |
|
Position of the catalog in a qualified table. Values are |
ub1 |
|
Does database support savepoints? Values are |
ub1 |
|
Does database support the nowait clause? Values are |
ub1 |
|
Is autocommit mode required for DDL statements? Values are |
ub1 |
|
Locking mode for the database. Values are |
ub1 |
7.2.15 Rule Attributes
Lists and describes the attributes when a parameter is for a rule.
Table 7-19 lists the attributes when a parameter is for a rule (type OCI_PTYPE_RULE
).
Table 7-19 Attributes Specific to Rules
Attribute | Description | Attribute Data Type |
---|---|---|
|
Rule condition |
OraText * |
|
Owner name of the evaluation context associated with the rule, if any |
OraText * |
|
Object name of the evaluation context associated with the rule, if any |
OraText * |
|
Comment associated with the rule, if any |
OraText * |
|
List of name-value pairs in the action context (type |
void * |
7.2.16 Rule Set Attributes
Lists and describes the attributes when a parameter is for a rule set.
Table 7-20 lists the attributes when a parameter is for a rule set (type OCI_PTYPE_RULE_SET
).
Table 7-20 Attributes Specific to Rule Sets
Attribute | Description | Attribute Data Type |
---|---|---|
|
Owner name of the evaluation context associated with the rule set, if any |
OraText * |
|
Object name of the evaluation context associated with the rule set, if any |
OraText * |
|
Comment associated with the rule set, if any |
OraText * |
|
List of rules in the rule set (type |
void * |
7.2.17 Evaluation Context Attributes
Lists and describes the attributes when a parameter is for an evaluation context.
Table 7-21 lists the attributes when a parameter is for an evaluation context (type OCI_PTYPE_EVALUATION_CONTEXT
).
Table 7-21 Attributes Specific to Evaluation Contexts
Attribute | Description | Attribute Data Type |
---|---|---|
|
Evaluation function associated with the evaluation context, if any |
OraText * |
|
Comment associated with the evaluation context, if any |
OraText * |
|
List of table aliases in the evaluation context (type |
void * |
|
List of variable types in the evaluation context (type |
void * |
7.2.18 Table Alias Attributes
Lists and describes the attributes when a parameter is for a table alias.
Table 7-22 lists the attributes when a parameter is for a table alias (type OCI_PTYPE_TABLE_ALIAS
).
Table 7-22 Attributes Specific to Table Aliases
Attribute | Description | Attribute Data Type |
---|---|---|
|
Table alias name |
OraText * |
|
Table name associated with the alias |
OraText * |
7.2.19 Variable Type Attributes
Lists and describes the attributes when a parameter is for a variable.
Table 7-23 lists the attributes when a parameter is for a variable (type OCI_PTYPE_VARIABLE_TYPE
).
Table 7-23 Attributes Specific to Variable Types
Attribute | Description | Attribute Data Type |
---|---|---|
|
Variable name |
OraText * |
|
Variable type |
OraText * |
|
Variable value function associated with the variable, if any |
OraText * |
|
Variable method function associated with the variable, if any |
OraText * |
7.2.20 Name Value Attributes
Lists and describes the attributes when a parameter is for a name-value pair.
Table 7-24 lists the attributes when a parameter is for a name-value pair (type OCI_PTYPE_NAME_VALUE
).
Table 7-24 Attributes Specific to Name-Value Pair
Attribute | Description | Attribute Data Type |
---|---|---|
|
Name |
OraText * |
|
Value |
OCIAnyData* |
7.3 Character-Length Semantics Support in Describe Operations
Query and column information are supported with character-length semantics.
Since release Oracle9i, query and column information are supported with character-length semantics.
The following attributes of describe handles support character-length semantics:
-
OCI_ATTR_CHAR_SIZE
gets the column character length, which is the number of characters allowed in the column. It is the counterpart ofOCI_ATTR_DATA_SIZE
, which gets the byte length. -
Calling
OCIAttrGet()
with attributeOCI_ATTR_CHAR_SIZE
orOCI_ATTR_DATA_SIZE
does not return data on stored procedure parameters, because stored procedure parameters are not bounded. -
OCI_ATTR_CHAR_USED
gets the type of length semantics of the column. Zero (0) means byte-length semantics and 1 means character-length semantics.
An application can describe a select-list query either implicitly or explicitly through OCIStmtExecute()
. Other schema elements must be described explicitly through OCIDescribeAny()
.
See Also:
7.3.1 Implicit Describing
If the database column was created using character-length semantics, then the implicit describe information contains the character length, the byte length, and a flag indicating how the database column was created.
OCI_ATTR_CHAR_SIZE
is the character length of the column or expression. The OCI_ATTR_CHAR_USED
flag is 1 in this case, indicating that the column or expression was created with character-length semantics.
The OCI_ATTR_DATA_SIZE
value is always large enough to hold all the data, as many as OCI_ATTR_CHAR_SIZE
number of characters. The OCI_ATTR_DATA_SIZE
is usually set to (OCI_ATTR_CHAR_SIZE
)*(the client's maximum number of bytes) for each character value.
If the database column was created with byte-length semantics, then for the implicit describe (it behaves exactly as it does before release 9.0) the OCI_ATTR_DATA_SIZE
value returned is (column's byte length)*(the maximum conversion ratio between the client and server's character set). That is, the column byte length divided by the server's maximum number of bytes for each character multiplied by the client's maximum number of bytes for each character. The OCI_ATTR_CHAR_USED
value is 0 and the OCI_ATTR_CHAR_SIZE
value is set to the same value as OCI_ATTR_DATA_SIZE
.
7.3.2 Explicit Describing
Explicit describes of tables have three attributes: OCI_ATTR_DATA_SIZE
, OCI_ATTR_CHAR_SIZE
, and OCI_ATTR_CHAR_USED
.
Explicit describes of tables have the following attributes:
-
OCI_ATTR_DATA_SIZE
gets the column's size in bytes, as it appears in the server -
OCI_ATTR_CHAR_SIZE
indicates the length of the column in characters -
OCI_ATTR_CHAR_USED
, is a flag that indicates how the column was created, as described previously in terms of the type of length semantics of the column
When inserting, if the OCI_ATTR_CHAR_USED
flag is set, you can set the OCI_ATTR_MAXCHAR_SIZE
in the bind handle to the value returned by OCI_ATTR_CHAR_SIZE
in the parameter handle. This prevents you from violating the size constraint for the column.
This section includes the following topic: Client and Server Compatibility Issues for Describing.
See Also:
7.3.2.1 Client and Server Compatibility Issues for Describing
Character-length semantics depends on the release of the server or client. It is best described when both server and client are Oracle9i or later. Otherwise, compatibility issues as described result.
When an Oracle9i or later client talks to an Oracle8i or earlier server, it behaves as if the database is only using byte-length semantics.
When an Oracle8i or earlier client talks to a Oracle9i or later server, the attributes OCI_ATTR_CHAR_SIZE
and OCI_ATTR_CHAR_USED
are not available on the client side.
In both cases, the character-length semantics cannot be described when either the server or client has an Oracle8i or earlier software release.
7.4 Examples Using OCIDescribeAny()
The following examples demonstrate the use of OCIDescribeAny()
for describing different types of schema objects.
For a more detailed code sample, see the demonstration program cdemodsa.c
included with your Oracle Database installation.
- Describing with Boolean Data Type Columns
-
Retrieving the Collection Element's Data Type of a Named Collection Type
-
Describing Each Column to Know Whether It Is an Invisible Column
See Also:
-
OCI Demonstration Programs for additional information about the demonstration programs
7.4.1 Describing with Boolean Data Type Columns
Describing on a table with boolean data type columns.
When you do a describe on a table with boolean Data Type columns,
external datatype code SQLT_BOL
is returned. This function also
returns the maximum data size and the display size for boolean data type from the
server. The maximum data size returned for boolean is 1byte, whereas the display
size for boolean is 11bytes. SQLplus uses the display size to display
TRUE
or FALSE
as string and for converting the
boolean true to false to string TRUE
or FALSE
.
Example 7-2 Support for Boolean Data Type
text tblName[] = "BoolTable”; /* the name of a table to be described */
if (OCIDescribeAny(svch, errh, (void *)tblName, sizeof(tblName), OCI_OTYPE_NAME, 0,OCI_PTYPE_TABLE, dschp))
return OCI_ERROR;
/* get the parameter handle */
if (OCIAttrGet((void *)dschp, OCI_HTYPE_DESCRIBE, (void *)&parmh, (ub4 *)0, OCI_ATTR_PARAM, errh))
return OCI_ERROR;
/* The type information of the object, in this case, OCI_PTYPE_TABLE,
is obtained from the parameter descriptor returned by the OCIAttrGet(). */
/* get the number of columns in the table */
numcols = 0;
if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&numcols, (ub4 *)0, OCI_ATTR_NUM_COLS, errh))
return OCI_ERROR;
…
…
/* go through the column list and retrieve the data type of each column,
and then recursively describe column types. */
for (i = 1; i <= numcols; i++)
{
/* for example, get data type for ith column */
coltyp = 0;
if (OCIAttrGet((void *)colhd, OCI_DTYPE_PARAM, (void *)&coltyp, (ub4 *)0,OCI_ATTR_DATA_TYPE, errh))
return OCI_ERROR;
if (coltype == SQLT_BOL)
printf(“Column type is boolean\n”);
/* get max data size */
if (OCIAttrGet((void *)colhd, OCI_DTYPE_PARAM, (void *)&colmaxsz, (ub4 *)0,OCI_ATTR_DATA_SIZE, errh))
return OCI_ERROR;
/* get display size */
if (OCIAttrGet((void *)colhd, OCI_DTYPE_PARAM, (void *)&coldispsz, (ub4 *)0,OCI_ATTR_DISP_SIZE, errh))
return OCI_ERROR;
}
7.4.2 Retrieving Column Data Types for a Table
Illustrates the use of an explicit describe that retrieves the column data types for a table.
Example 7-3 illustrates the use of an explicit describe that retrieves the column data types for a table.
Example 7-3 Using an Explicit Describe to Retrieve Column Data Types for a Table
... int i=0; text objptr[] = "EMPLOYEES"; /* the name of a table to be described */ ub2 numcols, col_width; ub1 char_semantics; ub2 coltyp; ub4 objp_len = (ub4) strlen((char *)objptr); OCIParam *parmh = (OCIParam *) 0; /* parameter handle */ OCIParam *collsthd = (OCIParam *) 0; /* handle to list of columns */ OCIParam *colhd = (OCIParam *) 0; /* column handle */ OCIDescribe *dschp = (OCIDescribe *)0; /* describe handle */ OCIHandleAlloc((void *)envhp, (void **)&dschp, (ub4)OCI_HTYPE_DESCRIBE, (size_t)0, (void **)0); /* get the describe handle for the table */ if (OCIDescribeAny(svch, errh, (void *)objptr, objp_len, OCI_OTYPE_NAME, 0, OCI_PTYPE_TABLE, dschp)) return OCI_ERROR; /* get the parameter handle */ if (OCIAttrGet((void *)dschp, OCI_HTYPE_DESCRIBE, (void *)&parmh, (ub4 *)0, OCI_ATTR_PARAM, errh)) return OCI_ERROR; /* The type information of the object, in this case, OCI_PTYPE_TABLE, is obtained from the parameter descriptor returned by the OCIAttrGet(). */ /* get the number of columns in the table */ numcols = 0; if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&numcols, (ub4 *)0, OCI_ATTR_NUM_COLS, errh)) return OCI_ERROR; /* get the handle to the column list of the table */ if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&collsthd, (ub4 *)0, OCI_ATTR_LIST_COLUMNS, errh)==OCI_NO_DATA) return OCI_ERROR; /* go through the column list and retrieve the data type of each column, and then recursively describe column types. */ for (i = 1; i <= numcols; i++) { /* get parameter for column i */ if (OCIParamGet((void *)collsthd, OCI_DTYPE_PARAM, errh, (void **)&colhd, (ub4)i)) return OCI_ERROR; /* for example, get data type for ith column */ coltyp = 0; if (OCIAttrGet((void *)colhd, OCI_DTYPE_PARAM, (void *)&coltyp, (ub4 *)0, OCI_ATTR_DATA_TYPE, errh)) return OCI_ERROR; /* Retrieve the length semantics for the column */ char_semantics = 0; OCIAttrGet((void*) colhd, (ub4) OCI_DTYPE_PARAM, (void*) &char_semantics,(ub4 *) 0, (ub4) OCI_ATTR_CHAR_USED, (OCIError *) errh); col_width = 0; if (char_semantics) /* Retrieve the column width in characters */ OCIAttrGet((void*) colhd, (ub4) OCI_DTYPE_PARAM, (void*) &col_width, (ub4 *) 0, (ub4) OCI_ATTR_CHAR_SIZE, (OCIError *) errh); else /* Retrieve the column width in bytes */ OCIAttrGet((void*) colhd, (ub4) OCI_DTYPE_PARAM, (void*) &col_width,(ub4 *) 0, (ub4) OCI_ATTR_DATA_SIZE, (OCIError *) errh); } if (dschp) OCIHandleFree((void *) dschp, OCI_HTYPE_DESCRIBE); ...
7.4.3 Describing the Stored Procedure
The steps required to describe type methods (also divided into functions and procedures) are identical to those of regular PL/SQL functions and procedures.
The difference between a procedure and a function is that the latter has a return type at position 0 in the argument list, whereas the former has no argument associated with position 0 in the argument list. Note that procedures and functions can take the default types of objects as arguments. Consider the following procedure:
P1 (arg1 emp.sal%type, arg2 emp%rowtype)
In Example 7-4, assume that each row in emp
table has two columns: name(VARCHAR2(20))
and sal(NUMBER)
. In the argument list for P1
, there are two arguments (arg1
and arg2
at positions 1 and 2, respectively) at level 0 and arguments (name
and sal
at positions 1 and 2, respectively) at level 1. Description of P1
returns the number of arguments as two while returning the higher level (> 0) arguments as attributes of the 0 zero level arguments.
Example 7-4 Describing the Stored Procedure
... int i = 0, j = 0; text objptr[] = "add_job_history"; /* the name of a procedure to be described */ ub4 objp_len = (ub4)strlen((char *)objptr); ub2 numargs = 0, numargs1, pos, level; text *name, *name1; ub4 namelen, namelen1; OCIParam *parmh = (OCIParam *) 0; /* parameter handle */ OCIParam *arglst = (OCIParam *) 0; /* list of args */ OCIParam *arg = (OCIParam *) 0; /* argument handle */ OCIParam *arglst1 = (OCIParam *) 0; /* list of args */ OCIParam *arg1 = (OCIParam *) 0; /* argument handle */ OCIDescribe *dschp = (OCIDescribe *)0; /* describe handle */ OCIHandleAlloc((void *)envhp, (void **)&dschp, (ub4)OCI_HTYPE_DESCRIBE, (size_t)0, (void **)0); /* get the describe handle for the procedure */ if (OCIDescribeAny(svch, errh, (void *)objptr, objp_len, OCI_OTYPE_NAME, 0, OCI_PTYPE_PROC, dschp)) return OCI_ERROR; /* get the parameter handle */ if (OCIAttrGet((void *)dschp, OCI_HTYPE_DESCRIBE, (void *)&parmh, (ub4 *)0, OCI_ATTR_PARAM, errh)) return OCI_ERROR; /* Get the number of arguments and the arg list */ if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&arglst, (ub4 *)0, OCI_ATTR_LIST_ARGUMENTS, errh)) return OCI_ERROR; if (OCIAttrGet((void *)arglst, OCI_DTYPE_PARAM, (void *)&numargs, (ub4 *)0, OCI_ATTR_NUM_PARAMS, errh)) return OCI_ERROR; /* For a procedure, you begin with i = 1; for a function, you begin with i = 0. */ for (i = 1; i <= numargs; i++) { OCIParamGet ((void *)arglst, OCI_DTYPE_PARAM, errh, (void **)&arg, (ub4)i); namelen = 0; OCIAttrGet((void *)arg, OCI_DTYPE_PARAM, (void *)&name, (ub4 *)&namelen, OCI_ATTR_NAME, errh); /* to print the attributes of the argument of type record (arguments at the next level), traverse the argument list */ OCIAttrGet((void *)arg, OCI_DTYPE_PARAM, (void *)&arglst1, (ub4 *)0, OCI_ATTR_LIST_ARGUMENTS, errh); /* check if the current argument is a record. For arg1 in the procedure arglst1 is NULL. */ if (arglst1) { numargs1 = 0; OCIAttrGet((void *)arglst1, OCI_DTYPE_PARAM, (void *)&numargs1, (ub4 *)0, OCI_ATTR_NUM_PARAMS, errh); /* Note that for both functions and procedures,the next higher level arguments start from index 1. For arg2 in the procedure, the number of arguments at the level 1 would be 2 */ for (j = 1; j <= numargs1; j++) { OCIParamGet((void *)arglst1, OCI_DTYPE_PARAM, errh, (void **)&arg1, (ub4)j); namelen1 = 0; OCIAttrGet((void *)arg1, OCI_DTYPE_PARAM, (void *)&name1, (ub4 *)&namelen1, OCI_ATTR_NAME, errh); } } } if (dschp) OCIHandleFree((void *) dschp, OCI_HTYPE_DESCRIBE); ...
7.4.4 Retrieving Attributes of an Object Type
Illustrates the use of an explicit describe on a named object type.
Example 7-5 illustrates the use of an explicit describe on a named object type. It illustrates how you can describe an object by its name or by its object reference (OCIRef
). The following code fragment attempts to retrieve the data type value of each of the object type's attributes.
Example 7-5 Using an Explicit Describe on a Named Object Type
... int i = 0; text type_name[] = "inventory_typ"; ub4 type_name_len = (ub4)strlen((char *)type_name); OCIRef *type_ref = (OCIRef *) 0; ub2 numattrs = 0, describe_by_name = 1; ub2 datatype = 0; OCITypeCode typecode = 0; OCIDescribe *dschp = (OCIDescribe *) 0; /* describe handle */ OCIParam *parmh = (OCIParam *) 0; /* parameter handle */ OCIParam *attrlsthd = (OCIParam *) 0; /* handle to list of attrs */ OCIParam *attrhd = (OCIParam *) 0; /* attribute handle */ /* allocate describe handle */ if (OCIHandleAlloc((void *)envh, (void **)&dschp, (ub4)OCI_HTYPE_DESCRIBE, (size_t)0, (void **)0)) return OCI_ERROR; /* get the describe handle for the type */ if (describe_by_name) { if (OCIDescribeAny(svch, errh, (void *)type_name, type_name_len, OCI_OTYPE_NAME, 0, OCI_PTYPE_TYPE, dschp)) return OCI_ERROR; } else { /* get ref to type using OCIAttrGet */ /* get the describe handle for the type */ if (OCIDescribeAny(svch, errh, (void*)type_ref, 0, OCI_OTYPE_REF, 0, OCI_PTYPE_TYPE, dschp)) return OCI_ERROR; } /* get the parameter handle */ if (OCIAttrGet((void *)dschp, OCI_HTYPE_DESCRIBE, (void *)&parmh, (ub4 *)0, OCI_ATTR_PARAM, errh)) return OCI_ERROR; /* The type information of the object, in this case, OCI_PTYPE_TYPE, is obtained from the parameter descriptor returned by OCIAttrGet */ /* get the number of attributes in the type */ if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&numattrs, (ub4 *)0, OCI_ATTR_NUM_TYPE_ATTRS, errh)) return OCI_ERROR; /* get the handle to the attribute list of the type */ if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&attrlsthd, (ub4 *)0, OCI_ATTR_LIST_TYPE_ATTRS, errh)) return OCI_ERROR; /* go through the attribute list and retrieve the data type of each attribute, and then recursively describe attribute types. */ for (i = 1; i <= numattrs; i++) { /* get parameter for attribute i */ if (OCIParamGet((void *)attrlsthd, OCI_DTYPE_PARAM, errh, (void **)&attrhd, i)) return OCI_ERROR; /* for example, get data type and typecode for attribute; note that OCI_ATTR_DATA_TYPE returns the SQLT code, whereas OCI_ATTR_TYPECODE returns the Oracle Type System typecode. */ datatype = 0; if (OCIAttrGet((void *)attrhd, OCI_DTYPE_PARAM, (void *)&datatype, (ub4 *)0, OCI_ATTR_DATA_TYPE,errh)) return OCI_ERROR; typecode = 0; if (OCIAttrGet((void *)attrhd, OCI_DTYPE_PARAM,(void *)&typecode, (ub4 *)0, OCI_ATTR_TYPECODE, errh)) return OCI_ERROR; /* if attribute is an object type, recursively describe it */ if (typecode == OCI_TYPECODE_OBJECT) { OCIRef *attr_type_ref; OCIDescribe *nested_dschp; /* allocate describe handle */ if (OCIHandleAlloc((void *)envh,(void**)&nested_dschp, (ub4)OCI_HTYPE_DESCRIBE,(size_t)0, (void **)0)) return OCI_ERROR; if (OCIAttrGet((void *)attrhd, OCI_DTYPE_PARAM, (void *)&attr_type_ref, (ub4 *)0, OCI_ATTR_REF_TDO,errh)) return OCI_ERROR; OCIDescribeAny(svch, errh,(void*)attr_type_ref, 0, OCI_OTYPE_REF, 0, OCI_PTYPE_TYPE, nested_dschp); /* go on describing the attribute type... */ } } if (dschp) OCIHandleFree((void *) dschp, OCI_HTYPE_DESCRIBE); ...
7.4.5 Retrieving the Collection Element's Data Type of a Named Collection Type
Illustrates the use of an explicit describe on a named collection type.
Example 7-6 illustrates the use of an explicit describe on a named collection type.
Example 7-6 Using an Explicit Describe on a Named Collection Type
text type_name[] = "phone_list_typ"; ub4 type_name_len = (ub4) strlen((char *)type_name); OCIRef *type_ref = (OCIRef *) 0; ub2 describe_by_name = 1; ub4 num_elements = 0; OCITypeCode typecode = 0, collection_typecode = 0, element_typecode = 0; void *collection_element_parmh = (void *) 0; OCIDescribe *dschp = (OCIDescribe *) 0; /* describe handle */ OCIParam *parmh = (OCIParam *) 0; /* parameter handle */ /* allocate describe handle */ if (OCIHandleAlloc((void *)envh, (void **)&dschp, (ub4)OCI_HTYPE_DESCRIBE, (size_t)0, (void **)0)) return OCI_ERROR; /* get the describe handle for the type */ if (describe_by_name) { if (OCIDescribeAny(svch, errh, (void *)type_name, type_name_len, OCI_OTYPE_NAME, 0, OCI_PTYPE_TYPE, dschp)) return OCI_ERROR; } else { /* get ref to type using OCIAttrGet */ /* get the describe handle for the type */ if (OCIDescribeAny(svch, errh, (void*)type_ref, 0, OCI_OTYPE_REF, 0, OCI_PTYPE_TYPE, dschp)) return OCI_ERROR; } /* get the parameter handle */ if (OCIAttrGet((void *)dschp, OCI_HTYPE_DESCRIBE, (void *)&parmh, (ub4 *)0, OCI_ATTR_PARAM, errh)) return OCI_ERROR; /* get the Oracle Type System type code of the type to determine that this is a collection type */ typecode = 0; if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM,(void *)&typecode, (ub4 *)0, OCI_ATTR_TYPECODE, errh)) return OCI_ERROR; /* if typecode is OCI_TYPECODE_NAMEDCOLLECTION, proceed to describe collection element */ if (typecode == OCI_TYPECODE_NAMEDCOLLECTION) { /* get the collection's type: OCI_TYPECODE_VARRAY or OCI_TYPECODE_TABLE */ collection_typecode = 0; if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, (void *)&collection_typecode, (ub4 *)0, OCI_ATTR_COLLECTION_TYPECODE, errh)) return OCI_ERROR; /* get the collection element; you MUST use this to further retrieve information about the collection's element */ if (OCIAttrGet((void *)parmh, OCI_DTYPE_PARAM, &collection_element_parmh, (ub4 *)0, OCI_ATTR_COLLECTION_ELEMENT, errh)) return OCI_ERROR; /* get the number of elements if collection is a VARRAY; not valid for nested tables */ if (collection_typecode == OCI_TYPECODE_VARRAY) { if (OCIAttrGet((void *)collection_element_parmh, OCI_DTYPE_PARAM, (void *)&num_elements, (ub4 *)0, OCI_ATTR_NUM_ELEMS, errh)) return OCI_ERROR; } /* now use the collection_element parameter handle to retrieve information about the collection element */ element_typecode = 0; if (OCIAttrGet((void *)collection_element_parmh, OCI_DTYPE_PARAM, (void *)&element_typecode, (ub4 *)0, OCI_ATTR_TYPECODE, errh)) return OCI_ERROR; /* do the same to describe additional collection element information; this is very similar to describing type attributes */ } if (dschp) OCIHandleFree((void *) dschp, OCI_HTYPE_DESCRIBE); ...
7.4.6 Describing with Character-Length Semantics
Shows a loop that retrieves the column names and data types corresponding to a query following query execution.
Example 7-7 shows a loop that retrieves the column names and data types corresponding to a query following query execution. The query was associated with the statement handle by a prior call to OCIStmtPrepare2().
Example 7-7 Using a Parameter Descriptor to Retrieve the Data Types, Column Names, and Character-Length Semantics
... OCIParam *mypard = (OCIParam *) 0; ub2 dtype; text *col_name; ub4 counter, col_name_len, char_semantics; ub2 col_width; sb4 parm_status; text *sqlstmt = (text *)"SELECT * FROM employees WHERE employee_id = 100"; checkerr(errhp, OCIStmtPrepare2(svchp, &stmthp, errhp, (OraText *)sqlstmt, (ub4)strlen((char *)sqlstmt), NULL, 0, (ub4) OCI_NTV_SYNTAX, (ub4) OCI_DEFAULT)); checkerr(errhp, OCIStmtExecute(svchp, stmthp, errhp, 0, 0, (OCISnapshot *)0, (OCISnapshot *)0, OCI_DEFAULT)); /* Request a parameter descriptor for position 1 in the select list */ counter = 1; parm_status = OCIParamGet((void *)stmthp, OCI_HTYPE_STMT, errhp, (void **)&mypard, (ub4) counter); /* Loop only if a descriptor was successfully retrieved for current position, starting at 1 */ while (parm_status == OCI_SUCCESS) { /* Retrieve the data type attribute */ checkerr(errhp, OCIAttrGet((void*) mypard, (ub4) OCI_DTYPE_PARAM, (void*) &dtype,(ub4 *) 0, (ub4) OCI_ATTR_DATA_TYPE, (OCIError *) errhp )); /* Retrieve the column name attribute */ col_name_len = 0; checkerr(errhp, OCIAttrGet((void*) mypard, (ub4) OCI_DTYPE_PARAM, (void**) &col_name, (ub4 *) &col_name_len, (ub4) OCI_ATTR_NAME, (OCIError *) errhp )); /* Retrieve the length semantics for the column */ char_semantics = 0; checkerr(errhp, OCIAttrGet((void*) mypard, (ub4) OCI_DTYPE_PARAM, (void*) &char_semantics,(ub4 *) 0, (ub4) OCI_ATTR_CHAR_USED, (OCIError *) errhp )); col_width = 0; if (char_semantics) /* Retrieve the column width in characters */ checkerr(errhp, OCIAttrGet((void*) mypard, (ub4) OCI_DTYPE_PARAM, (void*) &col_width, (ub4 *) 0, (ub4) OCI_ATTR_CHAR_SIZE, (OCIError *) errhp )); else /* Retrieve the column width in bytes */ checkerr(errhp, OCIAttrGet((void*) mypard, (ub4) OCI_DTYPE_PARAM, (void*) &col_width,(ub4 *) 0, (ub4) OCI_ATTR_DATA_SIZE, (OCIError *) errhp )); /* increment counter and get next descriptor, if there is one */ counter++; parm_status = OCIParamGet((void *)stmthp, OCI_HTYPE_STMT, errhp, (void **)&mypard, (ub4) counter); } /* while */ ...
7.4.7 Describing Each Column to Know Whether It Is an Invisible Column
Illustrates the use of invisible column properties and checking each column to determine if it is an invisible column.
The following code example illustrates the use of invisible column properties and checking each column to determine if it is an invisible column. See the OCI_ATTR_INVISIBLE_COL
attribute description in the table in Column Attributes for more information.
Example 7-8 Checking for Invisible Columns
..... ..... checkerr(errhp, OCIHandleAlloc((dvoid *) envhp, (dvoid **) &dschp, (ub4) OCI_HTYPE_DESCRIBE, (size_t) 0, (dvoid **) 0)); /* Set the invisible column attribute to get the invisible column(s). */ checkerr(errhp, OCIAttrSet(dschp, OCI_HTYPE_DESCRIBE, &invscols, 0, OCI_ATTR_SHOW_INVISIBLE_COLUMNS, errhp)); if ((retval = OCIDescribeAny(svchp, errhp, (dvoid *)tablename, (ub4) strlen((char *) tablename), OCI_OTYPE_NAME, (ub1)1, OCI_PTYPE_TABLE, dschp)) != OCI_SUCCESS) { if (retval == OCI_NO_DATA) { printf("NO DATA: OCIDescribeAny on %s\n", tablename); } else /* OCI_ERROR */ { printf( "ERROR: OCIDescribeAny on %s\n", tablename); checkerr(errhp, retval); return; } } else { ub1 colIsInv; /* Get the parameter descriptor. */ checkerr (errhp, OCIAttrGet((dvoid *)dschp, (ub4)OCI_HTYPE_DESCRIBE, (dvoid *)&parmp, (ub4 *)0, (ub4)OCI_ATTR_PARAM, (OCIError *)errhp)); /* Get the attributes of the table. */ checkerr (errhp, OCIAttrGet((dvoid*) parmp, (ub4) OCI_DTYPE_PARAM, (dvoid*) &objid, (ub4 *) 0, (ub4) OCI_ATTR_OBJID, (OCIError *)errhp)); /* Get the column list of the table. */ checkerr (errhp, OCIAttrGet((dvoid*) parmp, (ub4) OCI_DTYPE_PARAM, (dvoid*) &collst, (ub4 *) 0, (ub4) OCI_ATTR_LIST_COLUMNS, (OCIError *)errhp)); /* Get the number of columns. */ checkerr (errhp, OCIAttrGet((dvoid*) parmp, (ub4) OCI_DTYPE_PARAM, (dvoid*) &numcols, (ub4 *) 0, (ub4) OCI_ATTR_NUM_COLS, (OCIError *)errhp)); /* Now describe each column to know whether it is a invisible column or not. */ for (pos = 1; pos <= parmcnt; pos++) { /* Get the parameter descriptor for each column. */ checkerr (errhp, OCIParamGet((dvoid *)parmp, (ub4)OCI_DTYPE_PARAM, errhp, (dvoid *)&parmdp, (ub4) pos)); ..... ..... checkerr (errhp, OCIAttrGet((dvoid*) parmdp, (ub4) OCI_DTYPE_PARAM, (dvoid*) &colIsInv, (ub4 *) 0, (ub4) OCI_ATTR_INVISIBLE_COL, (OCIError *)errhp)); ..... ..... } } ..... .....