Simple Stored Procedures in Embedded SQL

You can create and call stored procedures in embedded SQL.

You can embed a CREATE PROCEDURE just like any other data definition statement, such as CREATE TABLE. You can also embed a CALL statement to execute a stored procedure. The following code fragment illustrates both creating and executing a stored procedure in embedded SQL:

EXEC SQL CREATE PROCEDURE pettycash( 
 IN Amount DECIMAL(10,2) )
BEGIN
 UPDATE account
 SET balance = balance - Amount
 WHERE name = 'bank';

 UPDATE account
 SET balance = balance + Amount
 WHERE name = 'pettycash expense';
END;
EXEC SQL CALL pettycash( 10.72 );

To pass host variable values to a stored procedure or to retrieve the output variables, you prepare and execute a CALL statement. The following code fragment illustrates the use of host variables. Both the USING and INTO clauses are used on the EXECUTE statement.

EXEC SQL BEGIN DECLARE SECTION;
double  hv_expense;
double  hv_balance;
EXEC SQL END DECLARE SECTION;

// Code here
EXEC SQL CREATE PROCEDURE pettycash(
   IN expense  DECIMAL(10,2),
   OUT endbalance DECIMAL(10,2) )
BEGIN
  UPDATE account
  SET balance = balance - expense
  WHERE name = 'bank';
  UPDATE account
  SET balance = balance + expense
  WHERE name = 'pettycash expense';

  SET endbalance = ( SELECT balance FROM account
         WHERE name = 'bank' );
END;

EXEC SQL PREPARE S1 FROM 'CALL pettycash( ?, ? )';
EXEC SQL EXECUTE S1 USING :hv_expense INTO :hv_balance;

• Stored Procedures with Result Sets
  Database procedures can also contain SELECT statements. The procedure is declared using a RESULT clause to specify the number, name, and types of the columns in the result set. Result set columns are different from output parameters. For procedures with result sets, the CALL statement can be used in place of a SELECT statement in the cursor declaration: