Dynamically Calling Anonymous Blocks

Syntax

Figure 1 shows the syntax diagram.

Figure 1 call_anonymous_block::=

Figure 2 shows the syntax diagram for using_clause.

Figure 2 using_clause::=

The above syntax diagram is explained as follows:

• The execute part of an anonymous block starts with a BEGIN statement, has a break with an END statement, and ends with a semicolon (;).
• USING [IN|OUT|IN OUT]bind_argument: specifies where the variable passed to the stored procedure parameter value is stored. The modifiers in front of bind_argument and of the corresponding parameter are the same.
• The input and output parameters in the middle of an anonymous block are designated by placeholders. The numbers of the placeholders and parameters are the same. The sequences of the parameters corresponding to the placeholders and the USING parameters are the same.
• Currently in GaussDB, when dynamic statements call anonymous blocks, placeholders cannot be used to pass input and output parameters in an EXCEPTION statement.
• Overloaded functions with placeholders cannot be called.
• The PERFORM keyword cannot be used to invoke a stored procedure when parameters are bound.
• Variables declared in an anonymous block and binding parameters cannot be used in the same statement at the same time.
• Only SQL statements invoked in anonymous blocks and stored procedures with OUT/INOUT parameters can be bound to parameters. For example, expressions and cursors are used in anonymous blocks, and dynamic statements are invoked in nested mode in anonymous blocks.

Examples

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--Create the stored procedure dynamic_proc.
gaussdb=# CREATE OR REPLACE PROCEDURE dynamic_proc
AS
   staff_id     NUMBER(6) := 200;
   first_name   VARCHAR2(20);
   salary       NUMBER(8,2);
BEGIN
    --Execute the anonymous block.
    EXECUTE IMMEDIATE 'begin select first_name, salary into :first_name, :salary from hr.staffs where staff_id= :dno; end;'
       USING OUT first_name, OUT salary, IN staff_id;
   dbe_output.print_line(first_name|| ' ' || salary);
END;
/

-- Invoke a stored procedure.
gaussdb=# CALL dynamic_proc();
mike 5800.00
 dynamic_proc 
--------------

(1 row)
-- Delete the stored procedure.
gaussdb=# DROP PROCEDURE dynamic_proc;