存储过程 - OUT 参数在选择时返回 null [英] Stored Procedure - OUT param returns null when selected

问题描述

我有一个 MySQL 存储过程，其中包含多个 IN 参数和一个 OUT.

I have a MySQL stored procedure with several IN params and one OUT.

DELIMITER $$
DROP PROCEDURE IF EXISTS create_or_update_post;
CREATE PROCEDURE create_or_update_post(IN user_login_id INT, IN postid VARCHAR(50), IN subject VARCHAR(150), IN postdate VARCHAR(50), IN body LONGTEXT, IN slug VARCHAR(50), OUT wp_post_id VARCHAR(50))
BEGIN
    IF EXISTS (SELECT @ID := `ID` FROM `wp_posts`, `wp_postmeta` WHERE `ID` = `post_id` AND `meta_key` = 'old_cs_id' AND `meta_value` = postid) THEN
        UPDATE `wp_posts`
        SET `post_title`=subject, `post_content`=body, `post_date`=postdate, `post_name`=slug, `post_author`=user_login_id, `post_modified`=(SELECT NOW())
        WHERE `ID` = @ID;
        SET wp_post_id = @ID;
    ELSE
        INSERT INTO `wp_posts` (`post_title`, `post_content`, `post_excerpt`, `to_ping`, `pinged`, `post_content_filtered`, `post_date`, `post_name`, `post_author`, `post_modified`, `post_status`)
        VALUES (subject, body, '', '', '', '', postdate, slug, user_login_id, (SELECT NOW()),'draft');

        /* Create metadata */
        SET wp_post_id = LAST_INSERT_ID();

        INSERT INTO `wp_postmeta` (`post_id`,`meta_key`,`meta_value`) VALUES(wp_post_id, 'old_cs_id', postid);

    END IF;
END$$
DELIMITER ;

当我调用过程并尝试 SELECT 变量时，我得到 null.

When I call the procedure and try to SELECT the variable, I get null.

CALL create_or_update_post(@user_login_id, '123', 'Some title', '2010-09-03 12:39:00', 'Some content', 'Blog Post', @wp_post_id);
SELECT @wp_post_id AS get_returned_post;

返回:

@wp_post_id
NULL

为什么我的 OUT 参数总是 NULL?

Why is my OUT param always NULL?

推荐答案

这是程序员尝试创建 MySQL 存储过程时发生的情况.此问题是由于尝试从 IF EXISTS 语句中的查询设置 @ID 变量造成的.

This is what happens when a programmer tries to create a MySQL stored procedure. This issue was a result from trying to set the @ID variable from a query in the IF EXISTS statement.

我重写了以下内容，现在我可以获得wp_post_id.

I rewrote the following and now I am able to get the wp_post_id.

DELIMITER $$
DROP PROCEDURE IF EXISTS create_or_update_post;
CREATE PROCEDURE create_or_update_post(IN user_login_id INT, IN postid VARCHAR(50), IN subject VARCHAR(150), IN postdate VARCHAR(50), IN body LONGTEXT, IN slug VARCHAR(50), OUT wp_post_id VARCHAR(50))
BEGIN
    IF EXISTS (SELECT * FROM `wp_posts`, `wp_postmeta` WHERE `ID` = `post_id` AND `meta_key` = 'old_cs_id' AND `meta_value` = postid) THEN
        SELECT @ID := `ID` FROM `wp_posts`, `wp_postmeta` WHERE `ID` = `post_id` AND `meta_key` = 'old_cs_id' AND `meta_value` = postid;
        UPDATE `wp_posts`
        SET `post_title`=subject, `post_content`=body, `post_date`=postdate, `post_name`=slug, `post_author`=user_login_id, `post_modified`=(SELECT NOW())
        WHERE `ID` = @ID;
        /* Update categories */
        SET wp_post_id = @ID;
    ELSE
        INSERT INTO `wp_posts` (`post_title`, `post_content`, `post_excerpt`, `to_ping`, `pinged`, `post_content_filtered`, `post_date`, `post_name`, `post_author`, `post_modified`, `post_status`)
        VALUES (subject, body, '', '', '', '', postdate, slug, user_login_id, (SELECT NOW()),'draft');

        /* Create metadata */
        SET wp_post_id = LAST_INSERT_ID();

        INSERT INTO `wp_postmeta` (`post_id`,`meta_key`,`meta_value`) VALUES(wp_post_id, 'old_cs_id', postid);
    END IF;
END$$
DELIMITER ;

*注意我通过复制IF EXISTS 语句中的查询并在其中设置@ID 所做的更改.

*Notice the change I made by duplicating the query in the IF EXISTS statement and setting the @ID within.

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