Stored Procedures

In the KWDB database, a stored procedure is a database object which stores complex programs issued with a single CALL statement. Stored procedures are SQL statement sets to complete specific functions. They are compiled, created, and saved in the KWDB database. You can call stored procedures by specifying their names and parameters.

KWDB supports creating, modifying, checking, removing, and calling stored procedures. Stored procedures supports all SQL statements and the following special syntax:

DECLARE
SET
SELECT, DELETE, INSERT, UPDATE INTO, UPSERT
OPEN, FETCH, CLOSE
CONTINUE HANDLER, EXIT HANDLER
IFELSE
LOOP
LABEL
LEAVE
Transaction statements
Special functions, such as (ROW_COUNT())

Note

Do not support nested stored procedures.
Do not support calling stored procedures within explicit transactions.
Do not support showing the execution plan of stored procedures using the EXPLAIN (ANALYZE) statement.
Do not support referencing other database objects except for relational and time-series tables within a stored procedure.
Do not support setting how to pass the values of parameters, such as IN, OUT, or INOUT. All parameters are passed as input parameters.
If there are multiple results sets within a stored procedure and some result sets are empty, the empty result sets are not displayed.
When connecting KWDB through the KaiwuDB JDBC Driver, only one result set is output in PREPARE mode.

CREATE PROCEDURE

The CREATE PROCEDURE statement creates a stored procedure.

Privileges

The user must be a member of the admin role or have been granted the related privileges on the objects referenced within the stored procedure body (such as the SELECT privilege on the specified table). By default, the root user belongs to the admin role.

Syntax

opt_proc_body
proc_set_stmt
proc_if_stmt
proc_while_stmt
simple_select_into_clause
proc_leave_stmt

Parameters

Parameter	Description
`proc_name`	The name of the stored procedure to create.
`parameter_list`	A comma-separated list of input parameter definitions of the stored procedure, in a format of `var_name var_type`. - `var_name`: the name of the variables. - `var_type`: the data type of the variables. Available options are INT2, INT4, INT8, FLOAT4, FLOAT8, DECIMAL, STRING, TEXT, CHAR, VARCHAR, TIMESTAMP, TIMESTAMPTZ. If not specified, it is set to NULL by default.
`opt_loop_label`	The label of the stored procedure body, in a format of `LABEL label_name:`.
`opt_proc_body`	The stored procedure body, including the SQL statements that must be executed when calling the stored procedure. The stored procedure body starts with the `BEGIN` keyword and ends with the `END` keyword. Note If you use KaiwuDB JDBC Driver to create a stored procedure, you should use the double dollars sign (`$$`) to wrap the `BEGIN ...END` statement.
`opt_label`	The label of the stored procedure body, in a format of `label_name`. The `opt_loop_label` and `opt_label` parameters must come in pairs.
`select_stmt`	The `SELECT` statement to read data from the database.
`insert_stmt`	The `INSERT` statement to insert one or more rows of data into tables.
`update_stmt`	The `UPDATE` statement to update one row of data into tables. It is in a format of `UPDATE .... RETURNING target_list INTO select_into_targets`.
`upsert_stmt`	The `UPSERT` statement to update and insert data into tables.
`delete_stmt`	The `DELETE` statement to remove one row of data from tables. It is in a format of`DELETE FROM .... RETURNING target_list INTO select_into_targets`.
`declare_stmt`	The `DECLARE` statement to declare user-defined variables, handlers, and cursors. For details, see Declarations.
`proc_set_stmt`	The `SET` statement to set values for user-defined variables. It is in a format of `SET var_name = a_expr`. - `var_name`: The name of the user-defined variable. - `a_expr`: The expression of values applied to user-defined variables.
`proc_if_stmt`	The `IF` statement to execute various SQL statement blocks based on the specified condition. It is in a format of `IF a_expr THEN proc_stmt_list opt_stmt_elsifs opt_stmt_else ENDIF`. - `a_expr`: The conditional expression of the `IF` statement. `a_expr` must be an expression that returns Boolean values. - `proc_stmt_list`: The SQL statement to execute after the condition is met. The SQL statements supported by the `IF` statement are identical to those supported by the `CREATE PROCEDURE` statement. - `opt_stmt_elsifs`: Optional. Other conditions of the `IF` statement. - `opt_stmt_else`: Optional. The `ELSE` condition of the `IF` statement.
`proc_while_stmt`	The `WHILE` statement to repeatedly execute codes when the specified condition is met. It is in a format of `opt_loop_label WHILE a_expr DO proc_stmt_list ENDWHILE opt_label`. - `opt_loop_label`: The label of the `WHILE` statement. -`a_expr`: The conditional expression of the `WHILE` statement. -`proc_stmt_list`: The SQL statement to execute after the condition is met. The SQL statements supported by the `WHILE` statement are identical to those supported by the `CREATE PROCEDURE` statement. - `opt_label`: The label of the `WHILE` statement, in a format of `label_name`. The `opt_loop_label` and `opt_label` parameters must come in pairs.
`begin_stmt`	The statement to begin a transaction.
`commit_stmt`	The statement to commit a transaction.
`rollback_stmt`	The statement to roll back a transaction.
`simple_select_into_clause`	The simple select statement in a format of `SELECT .... INTO select_into_targets from_clause ....`. `select_into_targets`: Support inserting a comma-separated list of variables, including user-defined variables.
`declare_cursor_stmt`	The statement to declare a cursor. For details, see Declare Cursors.
`open_cursor_stmt`	The statement to open a cursor. For details, see OPEN.
`fetch_cursor_stmt`	The statement to fetch a cursor. For details, see FETCH.
`close_cursor_stmt`	The statement to close a cursor. For details, see CLOSE.
`proc_leave_stmt`	When using the `LABEL` keyword to define labels for the stored procedure body or `WHILE` statement, you can use the `LEAVE` statement to step out the stored procedure body or the `WHILE` loop. It is in a format of `LEAVE label_name`.

Examples

This example creates a stored procedure named test.

-- Set the delimiter to double backslash.
delimiter \\

-- Create a stored procedure.
create procedure test() 
label test:
begin 
        declare a int;
        declare b int;
        declare err int;
        declare exit HANDLER FOR NOT FOUND,SQLEXCEPTION
        BEGIN
          SET err = -1;
          SELECT a,b;
          ROLLBACK;
        ENDHANDLER;
        
        START TRANSACTION;
        set a = 10;
        select a, b from t1;
        update t1 set a =  a + 1 where b > 0;
        insert into t1 values (a, b);
        label my_loop:
        WHILE b <= 10 DO 
                declare d int;
                set d = b + 2;
                if d > 9 then 
                        select * from t1; 
                        leave my_loop;
                elsif b > 5 then 
                        select * from t2; 
                endif;
                set b = b + 1; 
        ENDWHILE my_loop; 
        IF err = 0 THEN
                SELECT a,b;
        ENDIF;
        COMMIT;
end test\\
delimiter ;
CREATE PROCEDURE

CALL

The CALL statement calls a stored procedure.

Privileges

The user must be a member of the admin role or have been granted the EXECUTE privilege on the specified stored procedure(s) and related privileges on the objects referenced within the stored procedure body (such as the SELECT privilege on the specified table). By default, the root user belongs to the admin role.

Syntax

Parameters

Parameter	Description
`proc_name`	The name of the stored procedure to call.
`input_param_list`	A comma-separated list of input parameter definitions of the stored procedure. Note When calling a stored procedure, the number, order, and type of specified input parameters must match with those specified when creating the stored procedure.

Examples

This example calls a stored procedure named test1 to check the data in the stored procedure when the a parameter is set to 1.

-- Set the delimiter to double backslash.
DELIMITER \\

-- Create a stored procedure.
CREATE PROCEDURE test1(a int) 
label test:
begin 
    if a > 5 then 
        select a;
    else 
        select 5,4,3,2,1;
    endif;
end test \\

-- Set the delimiter to semicolon.
DELIMITER ;

-- Call the stored procedure.
call test1(1);
  ?column? | ?column? | ?column? | ?column? | ?column?
-----------+----------+----------+----------+-----------
         5 |        4 |        3 |        2 |        1

ALTER PROCEDURE

The ALTER PROCEDURE statement modifies comments of a specified stored procedure. You can also use the COMMENT ON statement to modify the comments of the specified stored procedure. For details, see COMMENT ON.

Privileges

The user must be a member of the admin role or have been granted the CREATE privilege on the specified stored procedure(s). By default, the root user belongs to the admin role.

Syntax

Parameters

Parameter	Description
`proc_name`	The name of the stored procedure to modify.
`comment_text`	The comment to be associated to the stored procedure.

Examples

This example adds comments to the proc1 stored procedure.

ALTER PROCEDURE proc1 COMMENT IS 'test query sql and if else logical';

SHOW PROCEDURES

The SHOW PROCEDURES statement lists all created stored procedures in the current KWDB database.

The SHOW CREATE PROCEDURE statement shows the CREATE PROCEDURE statement for an existing stored procedure and the parameters specified when creating the stored procedure.

Privileges

The user must have any privilege on the specified stored procedure(s).

Syntax

Show all created stored procedures
Show the CREATE PROCEDURE statement for an existing stored procedure

Parameters

Parameter	Description
`WITH COMMENT`	Optional. Show a stored procedure's comments.
`proc_name`	The name of the stored procedure to show.

Examples

Show all created stored procedures in the current KWDB database.

SHOW PROCEDURES;
procedure_name
------------------
proc1
(1 row)

Show all created stored procedures with comments in the current KWDB database.

SHOW PROCEDURES WITH COMMENT;
procedure_name |              comment
-----------------+-------------------------------------
proc1           | test query sql and if else logical
(1 row)

Show the CREATE PROCEDURE statement for a specified stored procedure.

SHOW CREATE PROCEDURE proc1;
procedure_name |                    procedure_body
-----------------+-------------------------------------------------------
proc1           | CREATE PROCEDURE proc1()
                | BEGIN
                |     DECLARE a INT4;
                |     DECLARE b INT4;
                |     DECLARE err INT4;
                |     DECLARE EXIT HANDLER FOR NOT FOUND,SQLEXCEPTION
                |     BEGIN
                |         SET err = -1;
                |         SELECT a, b;
                |         ROLLBACK TRANSACTION;
                |     ENDHANDLER;
                |     BEGIN TRANSACTION;
                |     SET a = 10;
                |     SELECT a, b FROM test.public.t1;
                |     UPDATE test.public.t1 SET a = a + 1 WHERE b > 0;
                |     INSERT INTO test.public.t1 VALUES (a, b);
                |     LABEL my_loop:
                |     WHILE b <= 10 DO
                |         DECLARE d INT4;
                |         SET d = b + 2;
                |         IF d > 9 THEN
                |         SELECT t1.a, t1.b FROM test.public.t1;
                |         LEAVE my_loop;
                |     ELSIF b > 5 THEN
                |         SELECT t2.a, t2.b, t2.c FROM test.public.t2;
                |     ENDIF;
                |         SET b = b + 1;
                |     ENDWHILE my_loop;
                |     IF err = 0 THEN
                |         SELECT a, b;
                |     ENDIF;
                |     COMMIT TRANSACTION;
                | END
(1 row)

DROP PROCEDURE

The DROP PROCEDURE statement removes a stored procedure.

Privileges

The user must be a member of the admin role or have been granted the DROP privilege on the specified stored procedure(s). By default, the root user belongs to the admin role.

Syntax

Parameters

Parameter Description

IF EXISTS Optional.
- When the IF EXISTS keyword is used, the system removes the stored procedure only if the stored procedure has already existed. Otherwise, the system fails to remove the stored procedure without returning an error.
- When the IF EXISTS keyword is not used, the system removes the stored procedure only if the stored procedure has already existed. Otherwise, the system fails to remove the stored procedure and returns an error.

proc_name The name of the stored procedure to remove.

Parameter	Description
`IF EXISTS`	Optional. - When the `IF EXISTS` keyword is used, the system removes the stored procedure only if the stored procedure has already existed. Otherwise, the system fails to remove the stored procedure without returning an error. - When the `IF EXISTS` keyword is not used, the system removes the stored procedure only if the stored procedure has already existed. Otherwise, the system fails to remove the stored procedure and returns an error.
`proc_name`	The name of the stored procedure to remove.

Examples

This example removes the proc1 stored procedure.

DROP PROCEDURE proc1;

# Stored Procedures

# CREATE PROCEDURE

# Privileges

# Syntax

# Parameters

# Examples

# CALL

# Privileges

# Syntax

# Parameters

# Examples

# ALTER PROCEDURE

# Privileges

# Syntax

# Parameters

# Examples

# SHOW PROCEDURES

# Privileges

# Syntax

# Parameters

# Examples

# DROP PROCEDURE

# Privileges

# Syntax

# Parameters

# Examples

Stored Procedures

CREATE PROCEDURE

Privileges

Syntax

Parameters

Examples

CALL

Privileges

Syntax

Parameters

Examples

ALTER PROCEDURE

Privileges

Syntax

Parameters

Examples

SHOW PROCEDURES

Privileges

Syntax

Parameters

Examples

DROP PROCEDURE

Privileges

Syntax

Parameters

Examples