Sybase 12.4.2 manual Control statements, 239, Dbisql and batches

CHAPTER 6 Using Procedures and Batches

DBISQL and batches

A list of semicolon-separated statements, such as the above, is parsed by DBISQL before it is sent to the server. In this case, DBISQL sends each statement individually to the server, not as a batch. Unless you have such parsing code in your application, the statements would be sent and treated as a batch. Putting a BEGIN and END around a set of statements causes DBISQL to treat them as a batch.

Many statements used in procedures can also be used in batches. You can use control statements (CASE, IF, LOOP, and so on), including compound statements (BEGIN and END), in batches. Compound statements can include declarations of variables, exceptions, temporary tables, or cursors inside the compound statement.

The following batch creates a table only if a table of that name does not already exist:

BEGIN

IF NOT EXISTS (

SELECT * FROM SYSTABLE

WHERE table_name = ’t1’ ) THEN CREATE TABLE t1 (

firstcol INT PRIMARY KEY, secondcol CHAR( 30 )

) ;

ELSE

MESSAGE ’Table t1 already exists’ ;

END IF

END

If you run this batch twice from DBISQL, it creates the table the first time you run it. The next time you run it, it prints the message in the server log file on Unix or on the server message window on Windows NT.

Control statements

There are a number of control statements for logical flow and decision making in the body of the procedure or in a batch. The following is a list of control statements available.

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