Mysql - procedure to get next auto increment

问题

I'm having some problems writing a stored procedure to get next value of Auto Incremented column. I want to be able to pass a table name and have the value returned to a specified variable.

The procedure is as follows:

CREATE PROCEDURE Find_last_AI(
        IN table_name VARCHAR(255),
        OUT last_AI INT)
BEGIN
    SELECT AUTO_INCREMENT
    INTO last_AI
    FROM  INFORMATION_SCHEMA.TABLES
    WHERE TABLE_SCHEMA = 'MySchema'
    AND   TABLE_NAME = table_name
    LIMIT 1;
END;

The problem is, after I call the function like this:

CALL Find_last_AI('MyTable', @out);    
SELECT @out;

I get the same wrong result - a numeric value (5) no matter what the table input is. The thing is, when I execute the code as a query the results yield correct values.

SELECT AUTO_INCREMENT
    FROM  INFORMATION_SCHEMA.TABLES
    WHERE TABLE_SCHEMA = 'MySchema'
    AND   TABLE_NAME   = 'table_name'
    LIMIT 1;

It seems that I'm forgetting something in the procedure itself, but I can't see it ?

回答1:

I tried myself like below and it worked fine.

set @tabname = 'tab';

    SELECT AUTO_INCREMENT
    INTO @incre
    FROM  INFORMATION_SCHEMA.TABLES
    WHERE TABLE_NAME = @tabname
    LIMIT 1;

select @incre;

Also Good to mention that, using the query above you will get the next (future) auto_increment value (nothing but, present value + 1).

EDIT:

Finally got it; problem is with LIMIT 1 in your query. Try the below code and it's guaranteed to work fine (TESTED). Also, don't use any reserved word as variable name.

DELIMITER $$
CREATE PROCEDURE Find_last_AI(IN tname VARCHAR(255), OUT last_AI INT)
BEGIN
    SELECT AUTO_INCREMENT
    INTO last_AI
    FROM  INFORMATION_SCHEMA.TABLES
    WHERE TABLE_SCHEMA = 'test'
    AND   TABLE_NAME = tname;
END$$
DELIMITER ;

Run the procedure like

CALL Find_last_AI('test3', @last_AI);    
SELECT @last_AI;

回答2:

to add the value auto_increment you must do it within the procedure, getting the last id and add 1, is a somewhat valid solution I leave SP:

#SP 
DELIMITER $$
CREATE OR REPLACE PROCEDURE set_Estados(in Estado VARCHAR(45))
    BEGIN
        DECLARE validar INT;
        DECLARE ID INT;
        SELECT COUNT(*) INTO validar FROM table_name WHERE table_row=Estado;
        if validar = 0 THEN
            SELECT (max(estados_id)+1) INTO ID FROM table_name limit 1;
            #the value estados_id its a auto_increment value, just call to add the value...
            INSERT INTO table_name(estados_id,estados_estado) VALUES(ID,Estado);
            CALL get_Estados(); #SP that show all data...
        ELSE
            SELECT CONCAT('El Estado: ',Estado,' ya existe.') ESTADO;
        END IF;
    END$$
DELIMITER ;

CALL set_Estados('Activo');

来源：https://stackoverflow.com/questions/23716915/mysql-procedure-to-get-next-auto-increment

标签

mysql

stored-procedures

auto-increment