Local Variables

Local variables are declared by the user, and can be used in procedures or in batches of SQL statements to hold information.

Local variables are declared using the DECLARE statement, which can be used only within a compound statement (that is, bracketed by the BEGIN and END keywords). The variable is initially set as NULL. You can set the value of the variable using the SET statement, or you can assign the value using a SELECT statement with an INTO clause.

The syntax of the DECLARE statement is as follows:

DECLARE variable-name data-type

You can pass local variables as arguments to procedures, as long as the procedure is called from within the compound statement.

Examples

The following batch illustrates the use of local variables:
```
BEGIN
	DECLARE local_var INT ;
	SET local_var = 10 ;
	MESSAGE 'local_var = ', local_var ;
END
```
Running this batch from ISQL displays this message on the server window:
```
local_var = 10
```
The variable local_var does not exist outside the compound statement in which it is declared. The following batch is invalid, and displays a column not found error:
```
-- This batch is invalid.
BEGIN
	DECLARE local_var INT ;
	SET local_var = 10 ;
	MESSAGE 'local_var = ', local_var ;
END;
MESSAGE 'local_var = ', local_var ;
```
The following example illustrates the use of SELECT with an INTO clause to set the value of a local variable:
```
BEGIN
	DECLARE local_var INT ;
	SELECT 10 INTO local_var ;
	MESSAGE 'local_var = ', local_var ;
END
```
Running this batch from ISQL displays this message on the server window:
```
local_var = 10
```

Compatibility

Names—Adaptive Server Enterprise and Sybase IQ both support local variables. In Adaptive Server Enterprise, all variables must be prefixed with an @ sign. In Sybase IQ, the @ prefix is optional. To write compatible SQL, ensure all your variables have the @ prefix.

Scope—The scope of local variables differs between Sybase IQ and Adaptive Server Enterprise. Sybase IQ supports the use of the DECLARE statement to declare local variables within a batch. However, if the DECLARE is executed within a compound statement, the scope is limited to the compound statement.

Declaration—Only one variable can be declared for each DECLARE statement in Sybase IQ. In Adaptive Server Enterprise, more than one variable can be declared in a single statement.