Dynamically Calling Anonymous Blocks

This section describes how to execute anonymous blocks in dynamic statements. Append IN and OUT behind the EXECUTE IMMEDIATE...USING statement to input and output parameters.

Syntax

Figure 1 shows the syntax diagram.

Figure 1 call_anonymous_block::=
Click to enlarge

Figure 2 shows the syntax diagram for using_clause.

Figure 2 using_clause::=
Click to enlarge

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 number of placeholders must match the number of parameters. Placeholder names cannot contain quoted digits, characters, or strings. 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 call 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.
Output parameters cannot be bound when the SELECT INTO statement in an anonymous block calls FUNCTION/PROCEDURE that contains output parameters.
Only SQL statements called 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 called in nested mode in anonymous blocks.
When the dynamic_sql_check parameter is enabled and the number of placeholders is the same as the number of parameters, an error is reported if placeholders with the same name are used as anonymous block parameters. In this case, you need to rename the placeholders.

Examples

    
     
       
       
         gaussdb=# DROP SCHEMA IF EXISTS hr CASCADE;
gaussdb=# CREATE SCHEMA hr;
gaussdb=# SET CURRENT_SCHEMA = hr;
gaussdb=# CREATE TABLE staffs 
(
  staff_id NUMBER, 
  first_name VARCHAR2,
  salary NUMBER
);
gaussdb=# INSERT INTO staffs VALUES (200, 'mike', 5800);
gaussdb=# INSERT INTO staffs VALUES (201, 'lily', 3000);
gaussdb=# INSERT INTO staffs VALUES (202, 'john', 4400);

--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;
/

-- Call the stored procedure.
gaussdb=# CALL dynamic_proc();
mike 5800.00
 dynamic_proc 
--------------

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

-- Example of an error reported when dynamic_sql_check is enabled
gaussdb=# SET behavior_compat_options = 'dynamic_sql_check';
SET
gaussdb=# CREATE OR REPLACE PROCEDURE test_proc_exception001(a out integer, b inout integer, c integer) 
as 
BEGIN
 a := 1; 
 begin b := 1/0; end; 
EXCEPTION
 WHEN others THEN
  b := 2; 
END;
/
CREATE PROCEDURE
gaussdb=# 
DECLARE 
 a integer := 1; 
 c integer; 
BEGIN
  execute immediate 'begin test_proc_exception001(:1,:2,:1); end;' using in out a, out c, a; 
END;
/
ERROR:  argnum not match in Dynamic SQL, using args num : 3 , actual sql args num : 2
CONTEXT:  PL/pgSQL function inline_code_block line 4 at EXECUTE statement
-- Change the placeholders with the same name.
gaussdb=# 
DECLARE 
 a integer := 1; 
 c integer; 
BEGIN
  execute immediate 'begin test_proc_exception001(:1,:2,:3); end;' using in out a, out c, a; 
END;
/
ANONYMOUS BLOCK EXECUTE
gaussdb=# DROP PROCEDURE test_proc_exception001;
DROP PROCEDURE
gaussdb=# reset behavior_compat_options;

        

      

    
   