Statement Functions

This section describes the statement functions.

Table 17-2 Statement Functions  

Function Purpose

OCIStmtExecute()

Sends statements to server for execution

OCIStmtFetch()

Fetches rows from a query (deprecated)

OCIStmtFetch2()

Fetches rows from a query

OCIStmtGetPieceInfo()

Gets piece information for piecewise operations

OCIStmtPrepare()

Prepares a SQL or PL/SQL statement for execution.

OCIStmtPrepare2()

Prepares a SQL or PL/SQL statement for execution.

OCIStmtRelease()

Releases the statement handle.

OCIStmtSetPieceInfo()

Sets piece information for piecewise operations


OCIStmtExecute()

Purpose

This call associates an application request with a server.

Syntax

sword OCIStmtExecute ( OCISvcCtx           *svchp,
                       OCIStmt             *stmtp,
                       OCIError            *errhp,
                       ub4                 iters,
                       ub4                 rowoff,
                       const OCISnapshot   *snap_in,
                       OCISnapshot         *snap_out,
                       ub4                 mode );

Parameters

svchp (IN/OUT)

Service context handle.

stmtp (IN/OUT)

An statement handle. It defines the statement and the associated data to be executed at the server. It is invalid to pass in a statement handle that has bind of datatypes only supported in release 8.x or later when svchp points to an Oracle7 server.

errhp (IN/OUT)

An error handle you can pass to OCIErrorGet() for diagnostic information in the event of an error.

iters (IN)

For non-SELECT statements, the number of times this statement is executed is equal to iters - rowoff.

For SELECT statements, if iters is nonzero, then defines must have been done for the statement handle. The execution fetches iters rows into these predefined buffers and prefetches more rows depending upon the prefetch row count. If you do not know how many rows the SELECT statement will retrieve, set iters to zero.

This function returns an error if iters=0 for non-SELECT statements.

Note:

For array DML operations, set iters <= 32767 to get better performance.
rowoff (IN)

The starting index from which the data in an array bind is relevant for this multiple row execution.

snap_in (IN)

This parameter is optional. if supplied, must point to a snapshot descriptor of type OCI_DTYPE_SNAP. The contents of this descriptor must be obtained from the snap_out parameter of a previous call. The descriptor is ignored if the SQL is not a SELECT. This facility allows multiple service contexts to ORACLE to see the same consistent snapshot of the database's committed data. However, uncommitted data in one context is not visible to another context even using the same snapshot.

snap_out (OUT)

This parameter optional. if supplied, must point to a descriptor of type OCI_DTYPE_SNAP. This descriptor is filled in with an opaque representation which is the current ORACLE "system change number" suitable as a snap_in input to a subsequent call to OCIStmtExecute(). This descriptor should not be used longer than necessary in order to avoid "snapshot too old" errors.

mode (IN)

The modes are:

  • OCI_BATCH_ERRORS - See "Batch Error Mode", for information about this mode.

  • OCI_COMMIT_ON_SUCCESS - When a statement is executed in this mode, the current transaction is committed after execution, if execution completes successfully.

  • OCI_DEFAULT - Calling OCIStmtExecute() in this mode executes the statement. It also implicitly returns describe information about the select-list.

  • OCI_DESCRIBE_ONLY - This mode is for users who wish to describe a query prior to execution. Calling OCIStmtExecute() in this mode does not execute the statement, but it does return the select-list description. To maximize performance, it is recommended that applications execute the statement in default mode and use the implicit describe which accompanies the execution.

  • OCI_EXACT_FETCH - Used when the application knows in advance exactly how many rows it will be fetching. This mode turns prefetching off for Oracle release 8 or later mode, and requires that defines be done before the execute call. Using this mode cancels the cursor after the desired rows are fetched and may result in reduced server-side resource usage.

  • OCI_PARSE_ONLY - This mode allows the user to parse the query prior to execution. Executing in this mode parses the query and returns parse errors in the SQL, if any. Users must note that this will involve an additional round trip to the server. To maximize performance, it is recommended that the user execute the statement in the default mode which, as part of a bundled operation, parses the statement.

  • OCI_STMT_SCROLLABLE_READONLY - Required for the result set to be scrollable. The result set cannot be updated. See "Fetching Results". Cannot be used with any other mode.

The modes are not mutually exclusive and can be used together, except for OCI_STMT_SCROLLABLE_READONLY.

Comments

This function is used to execute a prepared SQL statement. Using an execute call, the application associates a request with a server.

If a SELECT statement is executed, the description of the select-list is available implicitly as a response. This description is buffered on the client side for describes, fetches and define type conversions. Hence it is optimal to describe a select list only after an execute.

Also for SELECT statements, some results are available implicitly. Rows will be received and buffered at the end of the execute. For queries with small row count, a prefetch causes memory to be released in the server if the end of fetch is reached, an optimization that may result in memory usage reduction. Set attribute call has been defined to set the number of rows to be prefetched for each result set.

For SELECT statements, at the end of the execute, the statement handle implicitly maintains a reference to the service context on which it is executed. It is the user's responsibility to maintain the integrity of the service context. The implicit reference is maintained until the statement handle is freed or the fetch is cancelled or an end of fetch condition is reached.

To re-execute a DDL statement, the statement needs to be re-prepared using OCIStmtPrepare() or OCIStmtPrepare2().

Note:

If output variables are defined for a SELECT statement before a call to OCIStmtExecute(), the number of rows specified by iters will be fetched directly into the defined output buffers and additional rows equivalent to the prefetch count will be prefetched. If there are no additional rows, then the fetch is complete without calling OCIStmtFetch().

Related Functions

OCIStmtPrepare()

OCIStmtFetch()

Purpose

Fetches rows from a query. Users are encouraged to use the new fetch call OCIStmtFetch2(). This call is deprecated.

Syntax

sword OCIStmtFetch ( OCIStmt     *stmtp,
                     OCIError    *errhp, 
                     ub4         nrows,
                     ub2         orientation,
                     ub4         mode );

Parameters

stmtp (IN)

A statement (application request) handle.

errhp (IN)

An error handle you can pass to OCIErrorGet() for diagnostic information in the event of an error.

nrows (IN)

Number of rows to be fetched from the current position.

orientation (IN)

Prior to release 9.0, the only acceptable value is OCI_FETCH_NEXT, which is also the default value.

mode (IN)

Pass as OCI_DEFAULT.

Comments

The fetch call is a local call, if prefetched rows suffice. However, this is transparent to the application.

If LOB columns are being read, LOB locators are fetched for subsequent LOB operations to be performed on these locators. Prefetching is turned off if LONG columns are involved.

This function can return OCI_NO_DATA on EOF and OCI_SUCCESS_WITH_INFO when one of the following errors occur:

  • ORA-24344 Success with compilation error

  • ORA-24345 A truncation or NULL fetch error occurred

  • ORA-24347 Warning of a NULL column in an aggregate function

If you call OCIStmtFetch() with the nrows parameter set to 0, this cancels the cursor.

Use OCI_ATTR_ROWS_FETCHED to find the number of rows that were successfully fetched into the user's buffers in the last fetch call.

Related Functions

OCIStmtExecute()

OCIStmtFetch2()

Purpose

This fetches a row from the (scrollable) result set. You are encouraged to use this fetch call instead of the deprecated call OCIStmtFetch().

Syntax

sword OCIStmtFetch2 ( OCIStmt     *stmthp,
                      OCIError    *errhp, 
                      ub4         nrows,
                      ub2         orientation,
                      sb4         fetchOffset,
                      ub4         mode );

Parameters

stmthp (IN/OUT)

This is the statement handle of the (scrollable) result set.

errhp (IN/OUT)

An error handle you can pass to OCIErrorGet() for diagnostic information in event of an error.

nrows (IN)

Number of rows to be fetched from the current position.

orientation (IN)

The acceptable values are:

  • OCI_DEFAULT - has the same effect as OCI_FETCH_NEXT

  • OCI_FETCH_CURRENT - gets the current row.

  • OCI_FETCH_NEXT - gets the next row from the current position. It is the default (has the same effect as OCI_DEFAULT). Use for a non-scrollable statement handle.

  • OCI_FETCH_FIRST - gets the first row in the result set.

  • OCI_FETCH_LAST - gets the last row in the result set.

  • OCI_FETCH_PRIOR - positions the result set on the previous row from the current row in the result set. You can fetch multiple rows using this mode, from the "previous row" also.

  • OCI_FETCH_ABSOLUTE will fetch the row number (specified by fetchOffset parameter) in the result set using absolute positioning.

  • OCI_FETCH_RELATIVE will fetch the row number (specified by fetchOffset parameter) in the result set using relative positioning.

fetchOffset (IN)

The offset to be used with the orientation parameter for changing the current row position.

mode (IN)

Pass in OCI_DEFAULT.

Comments

The fetch call works similarly to the OCIStmtFetch() call with the addition of the fetchOffset parameter. It can be used on any statement handle, whether it is scrollable or not. For a non-scrollable statement handle, the only acceptable value of orientation is OCI_FETCH_NEXT, and the fetchOffset parameter will be ignored.

For new applications you are encouraged to use this new call, OCIStmtFetch2().

A fetchOffset with orientation set to OCI_FETCH_RELATIVE is equivalent to all of the following:

  • OCI_FETCH_CURRENT with a value of fetchOffset equal to 0,

  • OCI_FETCH_NEXT with a value of fetchOffset equal to 1,

  • OCI_FETCH_PRIOR with a value of fetchOffset equal to -1.

OCI_ATTR_ROW_COUNT contains the highest absolute row value that was fetched.

All other orientation modes besides OCI_FETCH_ABSOLUTE and OCI_FETCH_RELATIVE will ignore the fetchOffset value.

This call can also be used to find out the number of rows in the result set by using OCI_FETCH_LAST, and then calling OCIAttrGet() on OCI_ATTR_CURRENT_POSITION. But the response time of this call can be high.

The return codes are the same as for OCIStmtFetch(), except that OER(1403) with return code OCI_NO_DATA will be returned every time a fetch on a scrollable statement handle (or execute) is made and not all rows requested by the application could be fetched.

If you call OCIStmtFetch2() with the nrows parameter set to 0, this cancels the cursor.

The scrollable statement handle will need to be explicitly cancelled (that is, fetch with 0 rows) or freed in order to release server-side resources for the scrollable cursor. A non-scrollable statement handle is implicitly cancelled on receiving the OER(1403).

Use OCI_ATTR_ROWS_FETCHED to find the number of rows that were successfully fetched into the user's buffers in the last fetch call.

See Also:

"Scrollable Cursors in OCI" for more information on this topic

Related Functions

OCIStmtExecute(), OCIBindByPos()

OCIStmtGetPieceInfo()

Purpose

Returns piece information for a piecewise operation.

Syntax

sword OCIStmtGetPieceInfo( const OCIStmt  *stmtp,
                           OCIError       *errhp,
                           void           **hndlpp,
                           ub4            *typep,
                           ub1            *in_outp,
                           ub4            *iterp, 
                           ub4            *idxp,
                           ub1            *piecep );

Parameters

stmtp (IN)

The statement when executed returned OCI_NEED_DATA.

errhp (OUT)

An error handle you can pass to OCIErrorGet() for diagnostic information in the event of an error.

hndlpp (OUT)

Returns a pointer to the bind or define handle of the bind or define whose runtime data is required or is being provided.

typep (OUT)

The type of the handle pointed to by hndlpp: OCI_HTYPE_BIND (for a bind handle) or OCI_HTYPE_DEFINE (for a define handle).

in_outp (OUT)

Returns OCI_PARAM_IN if the data is required for an IN bind value. Returns OCI_PARAM_OUT if the data is available as an OUT bind variable or a define position value.

iterp (OUT)

Returns the row number of a multiple row operation.

idxp (OUT)

The index of an array element of a PL/SQL array bind operation.

piecep (OUT)

Returns one of the following defined values OCI_ONE_PIECE, OCI_FIRST_PIECE, OCI_NEXT_PIECE and OCI_LAST_PIECE.

Comments

When an execute or fetch call returns OCI_NEED_DATA to get or return a dynamic bind or define value or piece, OCIStmtGetPieceInfo() returns the relevant information: bind or define handle, iteration, index number and which piece.

See Also:

"Runtime Data Allocation and Piecewise Operations in OCI" for more information about using OCIStmtGetPieceInfo().

OCIStmtPrepare()

Purpose

This call prepares a SQL or PL/SQL statement for execution.

Syntax

sword OCIStmtPrepare ( OCIStmt       *stmtp,
                       OCIError      *errhp,
                       const OraText *stmt, 
                       ub4           stmt_len,
                       ub4           language,
                       ub4           mode );

Parameters

stmtp (IN)

A statement handle associated with the statement to be executed. By default, it contains the encoding setting in the environment handle from which it is derived. A statement can be prepared in UTF-16 encoding only in a UTF-16 environment.

errhp (IN)

An error handle you can pass to OCIErrorGet() for diagnostic information in the event of an error.

stmt (IN)

SQL or PL/SQL statement to be executed. Must be a NULL-terminated string. That is, the ending character is a number of NULL bytes, depending on the encoding. The statement must be in the encoding specified by the charset parameter of a previous call to OCIEnvNlsCreate().

Always cast the parameter to (text *). After a statement has been prepared in UTF-16, the character set for the bind and define buffers will default to UTF-16.

stmt_len (IN)

Length of the statement in characters or in number of bytes, depending on the encoding. Must not be zero.

language (IN)

Specifies V7, or native syntax. Possible values are:

  • OCI_V7_SYNTAX - V7 ORACLE parsing syntax

  • OCI_NTV_SYNTAX - syntax depends upon the version of the server.

mode (IN)

Similar to the mode in the OCIEnvCreate() call, but this one has higher priority because it can override the "naturally" inherited mode setting.

The only possible value is:

  • OCI_DEFAULT - default mode. The statement handle stmtp uses whatever is specified by its parent environment handle.

Comments

An OCI application uses this call to prepare a SQL or PL/SQL statement for execution. The OCIStmtPrepare() call defines an application request.

The mode parameter determines whether the statement content is encoded as UTF-16 or not. The statement length is in number of codepoints or in number of bytes, depending on the encoding.

While the statement handle inherits the encoding setting from the parent environment handle, the mode for this call can also change the encoding setting for the statement handle itself.

Data values for this statement initialized in subsequent bind calls will be stored in a bind handle which use settings in this statement handle as default.

This call does not create an association between this statement handle and any particular server.

Before re-executing a DDL statement, call this function a second time.

See Also:

"Preparing Statements" for more information about using this call.

OCIStmtPrepare2()

Purpose

This call prepares a SQL or PL/SQL statement for execution. The user has the option of using the statement cache, if it has been enabled.

Syntax

sword OCIStmtPrepare2 ( OCISvcCtx      *svchp,
                        OCIStmt        **stmthp,
                        OCIError       *errhp,
                        const OraText  *stmttext,
                        ub4            stmt_len,
                        const OraText  *key,
                        ub4            keylen,
                        ub4            language,
                        ub4            mode );

Parameters

svchp (IN)

The service context to be associated with the statement.

errhp (IN)

A pointer to the error handle for diagnostics.

stmthp (OUT)

Pointer to the statement handle returned.

stmttext (IN)

The statement text. The semantics of the stmttext are same as that of OCIStmtPrepare(), that is, the string must be NULL-terminated.

stmt_len (IN)

The statement text length.

key (IN)

For statement caching only. The key to be used for searching the statement in the statement cache. If the key is passed in, then the statement text and other parameters are ignored and the search is solely based on the key.

keylen (IN)

For statement caching only. The length of the key.

language (IN)

Specifies V7, or native syntax. Possible values are:

  • OCI_V7_SYNTAX - V7 ORACLE parsing syntax

  • OCI_NTV_SYNTAX - syntax depends upon the version of the server.

mode (IN)

This function can be used with and without statement caching. This is determined at the time of connection or session pool creation. If caching is enabled for a session, then all statements in the session will have caching enabled, and if caching is not enabled, then all statements will not be cached.

The valid modes are:

  • OCI_DEFAULT - For non-caching, this is the only valid setting. If the statement is not found in the cache, it allocates a new statement handle and prepares the statement handle for execution. If it is not found and

    • only the text has been supplied: a new statement will be allocated and prepared and returned. The tag will be NULL. OCI_SUCCESS will be returned.

    • only the tag has been supplied: stmthp will be NULL. OCI_ERROR will be returned.

    • both text and key were supplied: a new statement will be allocated and prepared and returned. The tag will be NULL. OCI_SUCCESS_WITH_INFO will be returned, as the returned statement differs from the requested statement in that the tag is NULL.

  • OCI_PREP2_CACHE_SEARCHONLY - In this case, if the statement is not found (a NULL statement handle is returned), you must take further action. If the statement is found, OCI_SUCCESS will be returned. Otherwise, OCI_ERROR will be returned.

  • OCI_PREP2_GET_PLSQL_WARNINGS - If warnings are enabled in the session and the PL/SQL program is compiled with warnings, then OCI_SUCCESS_WITH_INFO will be the return status from the execution. Use OCIErrorGet() to find the new error number corresponding to the warnings.

Related Functions

OCIStmtRelease()

OCIStmtRelease()

Purpose

Releases the statement handle obtained by a call to OCIStmtPrepare2().

Syntax

sword OCIStmtRelease ( OCIStmt        *stmthp,  
                       OCIError       *errhp,
                       const OraText  *key,
                       ub4            keylen,
                       ub4            mode );  

Parameters

stmthp (IN/OUT)

The statement handle returned by OCIStmtPrepare2()

errhp (IN)

The error handle used for diagnostics.

key (IN)

Only valid for statement caching. This is a SQL string passed in by the caller. If a NULL key is passed in the statement will not be tagged.

keylen (IN)

Only valid for statement caching. The length of the key.

mode (IN)

The valid modes are

  • OCI_DEFAULT

  • OCI_STRLS_CACHE_DELETE - Only valid for statement caching. The statement will not be kept in the cache any more.

Related Functions

OCIStmtPrepare2()

OCIStmtSetPieceInfo()

Purpose

Sets piece information for a piecewise operation.

Syntax

sword OCIStmtSetPieceInfo ( void              *hndlp,
                            ub4               type,
                            OCIError          *errhp,
                            const void        *bufp,
                            ub4               *alenp, 
                            ub1               piece,
                            const void        *indp, 
                            ub2               *rcodep ); 

Parameters

hndlp (IN/OUT)

The bind/define handle.

type (IN)

Type of the handle.

errhp (OUT)

An error handle you can pass to OCIErrorGet() for diagnostic information in the event of an error.

bufp (IN/OUT)

A pointer to a storage containing the data value or the piece when it is an IN bind variable, otherwise bufp is a pointer to storage for getting a piece or a value for OUT binds and define variables. For named datatypes or REFs, a pointer to the object or REF is returned.

alenp (IN/OUT)

The length of the piece or the value. Do not change this parameter between executions of the same SQL statement.

piece (IN)

The piece parameter. Valid values:

  • OCI_ONE_PIECE

  • OCI_FIRST_PIECE

  • OCI_NEXT_PIECE

  • OCI_LAST_PIECE

This parameter is used for IN bind variables only.

indp (IN/OUT)

Indicator. A pointer to a sb2 value or pointer to an indicator structure for named datatypes (SQLT_NTY) and REFs (SQLT_REF), that is, *indp is either an sb2 or a void * depending upon the datatype.

rcodep (IN/OUT)

Return code.

Comments

When an execute call returns OCI_NEED_DATA to get a dynamic IN/OUT bind value or piece, OCIStmtSetPieceInfo() sets the piece information: the buffer, the length, which piece is currently being processed, the indicator, and the return code for this column.

See Also:

For more information about using OCIStmtSetPieceInfo() see the section "Runtime Data Allocation and Piecewise Operations in OCI"