mySQL 比较触发器中两个不同的列值

Question

我正在尝试触发检查 table 中的两个值是否相同，如果相同则将信息插入另一个 table。我的代码如下。

user_id 是一个 INT(10) post_author_id 是一个 VARCHAR(33) 8utf_unicode_ci

CASE
WHEN (new.user_id = (SELECT CAST(post_author_id AS UNSIGNED INTEGER) FROM Cvr_hooks_501_1000)) 
THEN
INSERT INTO Cvr_1_link_501_1000 (a_hook_id, a_user_id, a_post_id, a_post_author_id)

VALUES (new.hook_id, 
        new.user_id, 
        new.post_id, 
        new.post_author_id);

END CASE

感谢任何帮助！

Answer 1

您可以使用EXISTS检查用户是否已经存在

CREATE tABLE Cvr_hooks_501_1000(post_author_id vaRCHAR(39))

INSERT INTO Cvr_hooks_501_1000 VALUES ("1")

CREATE TABLE account(hook_id int, user_id int(11) ,post_id int, post_author_id int)

CREATE TABLE Cvr_1_link_501_1000 (a_hook_id int, a_user_id int(11) ,a_post_id int, a_post_author_id int)

CREATE TRIGGER upd_check AFTER  INSERT ON account
       FOR EACH ROW
       BEGIN
      IF ( EXISTS(SELECT 1 FROM Cvr_hooks_501_1000 WHERE post_author_id =  new.user_id)) then
          
          INSERT INTO Cvr_1_link_501_1000 (a_hook_id, a_user_id, a_post_id, a_post_author_id)

          VALUES (new.hook_id, 
                  new.user_id, 
                  new.post_id, 
                  new.post_author_id);

          END IF;

       END

INSERT INTO account VALUES(1,1,1,1)

SELECT * FROM Cvr_1_link_501_1000

a_hook_id | a_user_id | a_post_id | a_post_author_id
--------: | --------: | --------: | ---------------:
        1 |         1 |         1 |                1

db<>fiddle here

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