|Oracle® Database PL/SQL Language Reference
11g Release 1 (11.1)
|PDF · Mobi · ePub|
The block, which groups related declarations and statements, is the basic unit of a PL/SQL source program. It has an optional declarative part, a required executable part, and an optional exception-handling part. Declarations are local to the block and cease to exist when the block completes execution.
A block can appear either at schema level (as a top-level block) or inside another block (as a nested block). A block can contain another block wherever it can contain an executable statement.
Any scalar or user-defined PL/SQL data type specifier such as
Signals the start of the executable part of a PL/SQL block, which contains executable statements. A PL/SQL block must contain at least one executable statement (even just the
Declares a collection (index-by table, nested table, or varray). For the syntax of
collection_declaration, see Collection.
Declares a constant. For the syntax of
constant_declaration, see Constant.
Applies only to data types that can be constrained such as
NUMBER. For character data types, this specifies a maximum size in bytes. For numeric data types, this specifies a maximum precision and scale.
Declares an explicit cursor. For the syntax of
cursor_declaration, see Explicit Cursor.
Declares a cursor variable. For the syntax of
cursor_variable_declaration, see Cursor Variable Declaration.
Signals the start of the declarative part of a PL/SQL block, which contains local declarations. Items declared locally exist only within the current block and all its sub-blocks and are not visible to enclosing blocks. The declarative part of a PL/SQL block is optional. It is terminated implicitly by the keyword
BEGIN, which introduces the executable part of the block. For more information, see Declarations.
PL/SQL does not allow forward references. You must declare an item before referencing it in any other statements. Also, you must declare subprograms at the end of a declarative section after all other program items.
Signals the end of a PL/SQL block. It must be the last keyword in a block. Remember,
END does not signal the end of a transaction. Just as a block can span multiple transactions, a transaction can span multiple blocks. See PL/SQL Blocks.
Signals the start of the exception-handling part of a PL/SQL block. When an exception is raised, normal execution of the block stops and control transfers to the appropriate exception handler. After the exception handler completes, execution proceeds with the statement following the block. See PL/SQL Blocks.
If there is no exception handler for the raised exception in the current block, control passes to the enclosing block. This process repeats until an exception handler is found or there are no more enclosing blocks. If PL/SQL can find no exception handler for the exception, execution stops and an
exception error is returned to the host environment. For more information about exceptions, see Chapter 11, "Handling PL/SQL Errors."
Declares an exception. For the syntax of
exception_declaration, see Exception Handler.
Associates an exception with a sequence of statements, which is executed when that exception is raised. For the syntax of
exception_handler, see Exception Handler.
Declares a function. See Function Declaration and Definition.
An undeclared identifier that optionally labels a PL/SQL block or statement. If used,
label_name must be enclosed by double angle brackets and must appear at the beginning of the block or statement which it labels. Optionally, when used to label a block, the
label_name can also appear at the end of the block without the angle brackets. Multiple labels are allowed for a block or statement, but they must be unique for each block or statement.
A global identifier declared in an enclosing block can be redeclared in a sub-block, in which case the local declaration prevails and the sub-block cannot reference the global identifier unless you use a block label to qualify the reference. See Example 2-28, "Block with Multiple and Duplicate Labels".
Is the label name (without the delimiters << and >>).
Declares an instance of an object type. To create an object type, use the CREATE TYPE Statement.
Declare a procedure. See Procedure Declaration and Definition.
Declares a user-defined record. For the syntax of
record_declaration, see Record Definition.
An executable (not declarative) statement. A sequence of statements can include procedural statements such as
RAISE, SQL statements such as
UPDATE, and PL/SQL blocks. PL/SQL statements are free format. That is, they can continue from line to line if you do not split keywords, delimiters, or literals across lines. A semicolon (;) serves as the statement terminator.
A user-defined subtype that was defined using any scalar or user-defined PL/SQL data type specifier such as
Declares a variable. For the syntax of
variable_declaration, see Constant.
PL/SQL supports a subset of SQL statements that includes data manipulation, cursor control, and transaction control statements but excludes data definition and data control statements such as