尝试创建新触发器时出现SQL错误 [英] SQL error when trying to create new trigger

问题描述

当我尝试创建触发器时：

And when I try to create a trigger:

CREATE TRIGGER ctg_el_del 
AFTER DELETE ON ctg
FOR EACH ROW
BEGIN
DELETE FROM ctg
       where ctg.id_ctg = old.lft
            WHERE  cat.id_ctg = old.rgt;
END;

此错误显示：

ERROR:  syntax error at or near "BEGIN"
LINE 4: BEGIN
        ^

推荐答案

STEP 1：您需要创建返回类型为Trigger的函数，在该函数中应提及如下的SQL操作：

STEP 1 : You need to Create function that returns type Trigger in that function you should mention the SQL Operation like below:

CREATE FUNCTION trigger_function() RETURNS TRIGGER AS $$
BEGIN
    DELETE FROM ctg 
    WHERE ctg.id_ctg = old.lft
    AND   ctg.id_ctg = old.rgt;
END
$$
LANGUAGE plpgsql;

第2步：然后在表上创建触发器以在之后调用像这样删除：

STEP 2 : And then create the trigger on the table to call after delete like this:

CREATE TRIGGER ctg_el_del 
AFTER DELETE ON ctg
FOR EACH ROW
EXECUTE PROCEDURE trigger_function();

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