如何在 MySQL 的触发器中声明变量?因为我在执行几行代码时遇到错误

How to declare variable in trigger in MySQL ? As I am getting error while executing few lines for the code(如何在 MySQL 的触发器中声明变量?因为我在执行几行代码时遇到错误)

问题描述

我想在 MySql 中执行以下代码，但出现错误

I want to execute the following code in MySql but I am getting the error

CREATE TRIGGER CINEMAHALLNO_GENERATE_TRIGGER 
BEFORE INSERT ON CINEMA_HALLS
FOR EACH ROW
BEGIN
  DECLARE cnt DOUBLE;
  DECLARE next1 DOUBLE;
  SELECT COUNT(HALLNO) INTO cnt from CINEMA_HALLS;
  IF cnt > 0 AND cnt < 20 THEN
    SELECT MAX(HALLNO) INTO NEXT1 FROM CINEMA_HALLS;
    set next1=next1+1;
    SET :new.HALLNO=next;
  ELSEIF cnt = 0 THEN
    SET :new.HALLNO=1;
  end if;
  end;

输出错误:SQL查询:

Output Error: SQL query:

创建触发器 CINEMAHALLNO_GENERATE_TRIGGER在 CINEMA_HALLS 上插入之前每一行开始声明 cnt DOUBLEMySQL 说:文档

CREATE TRIGGER CINEMAHALLNO_GENERATE_TRIGGER BEFORE INSERT ON CINEMA_HALLS FOR EACH ROW BEGIN DECLARE cnt DOUBLE MySQL said: Documentation

推荐答案

Declare 必须放在 Begin 之后.请查看以下链接

Declare must be placed after the Begin. Please check the following link

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