我要实现的功能是：在更新一个表时，从三个表中查询记录并插入到另外一个表中，下面是我写触发器的过程：
第一次写的触发器如下：
CREATE TRIGGER istmingxi
AFTER UPDATE ON sys_shenbao FOR EACH ROW BEGIN
SELECT @kid:=jl.kid,@gonghao:=shen.gonghao,@vuid:=jl.vuid,@zhibiao:=ct.leibie,
@citiao:=ct.bianhao,@fenshu:=ct.fenshu,@bumen:=zl.bumen,@ctime:=shen.verifytime
FROM sys_shenbao shen
INNER JOIN sys_shenbjl jl ON jl.d = shen.sid
INNER JOIN sys_citiao ct ON ct.bianhao = shen.ctbh
INNER JOIN sys_jibzl zl ON zl.gonghao = shen.gonghao
WHERE shen.sid = new.sid;
if fenshu > 0 then
set @jiafen = fenshu;
set @jianfen = 0;
else
set @jiafen = 0;
set @jianfen = fenshu;
end if;
INSERT INTO sys_mingxi(`kid`,`gonghao`,`vuid`,`zhibiao`,`bumen`,`jiafen`,`jianfen`,`yue`,`ctime`)
VALUES(kid,gonghao,vuid,zhibiao,citiao,bumen,jiafen,jianfen,0,ctime);
END;
生成上面触发器时报错：Not allowed to return a result set from a trigger；原因是trigger 中不允许返回select出来的结果集，所以 “select @kid:=jl.kid....”部分改变成另一种写法，如下
CREATE TRIGGER istmingxi
AFTER UPDATE ON sys_shenbao FOR EACH ROW BEGIN
SELECT jl.skid into @kid, shen.gonghao into @gonghao,jl.vuid into @vuid,ct.leibie into @zhibiao,
ct.bianhao into @citiao,ct.fenshu into @fenshu,zl.bumen into @bumen,shen.verifytime into @ctime
FROM sys_shenbao shen
INNER JOIN sys_shenbjl jl ON jl.id = shen.sid
INNER JOIN sys_citiao ct ON ct.bianhao = shen.ctbh
INNER JOIN sys_jibzl zl ON zl.gonghao = shen.gonghao
WHERE shen.sid = new.sid;
if fenshu > 0 then
set @jiafen = fenshu;
set @jianfen = 0;
else
set @jiafen = 0;
set @jianfen = fenshu;
end if;
INSERT INTO sys_mingxi(`kid`,`gonghao`,`vuid`,`zhibiao`,`bumen`,`jiafen`,`jianfen`,`yue`,`ctime`)
VALUES(kid,gonghao,vuid,zhibiao,citiao,bumen,jiafen,jianfen,0,ctime);
END;
此时还是会报错：SQL 错误 [1327] [42000]: Undeclared variable: shen; Undeclared variable: shen;原因是“select jl.skic into @kid...”部分的select语句的语法还是不对。
原因是：欲想通过一个SELECT语句对多个变量赋值，请采用以下语句形式：SELECT id,name INTO @v1,@v2 FROM ...
所以最终我改成了如下的方式：
CREATE TRIGGER istmingxi
AFTER UPDATE ON sys_shenbao FOR EACH ROW BEGIN
SELECT jl.skid,shen.gonghao,jl.vuid,ct.leibie,ct.bianhao,ct.fenshu,zl.bumen,shen.verifytime
INTO @kid,@gonghao,@vuid,@zhibiao,@citiao,@fenshu,@bumen,@ctime
FROM sys_shenbao shen
INNER JOIN sys_shenbjl jl ON jl.id = shen.sid
INNER JOIN sys_citiao ct ON ct.bianhao = shen.ctbh
INNER JOIN sys_jibzl zl ON zl.gonghao = shen.gonghao
WHERE shen.sid = new.sid;
if fenshu > 0 then
set @jiafen = fenshu;
set @jianfen = 0;
else
set @jiafen = 0;
set @jianfen = fenshu;
end if;
INSERT INTO sys_mingxi(`kid`,`gonghao`,`vuid`,`zhibiao`,`bumen`,`jiafen`,`jianfen`,`yue`,`ctime`)
VALUES(kid,gonghao,vuid,zhibiao,citiao,bumen,jiafen,jianfen,0,ctime);
END;
到这运行的时候还是会报错：ERROR 1172 (42000): Result consisted of more than one row；
这个报错的原因是select into返回了多行记录，这在给变量赋值的时候是不允许的，后来检查是where条件的问题；
修改了where条件后返回一条记录这个问题解决了。
再次运行时又报错：SQL 错误 [1054] [42S22]: Unknown column 'fenshu' in 'field list' ；这个错误的原因是下面在引用变量“fenshu”时语法错误；
上面定义变量时用了@符号，下面引用时也要用上@符号。
最后触发器改成如下：
AFTER UPDATE ON sys_shenbao FOR EACH ROW BEGIN
if new.verifystatus = 2 then
SELECT jl.skid,shen.gonghao,jl.vuid,ct.leibie,ct.bianhao,ct.fenshu,zl.bumen,shen.verifytime
INTO @kid,@gonghao,@vuid,@zhibiao,@citiao,@fenshu,@bumen,@ctime
FROM sys_shenbao shen
INNER JOIN sys_shenbjl jl ON jl.id = shen.sid
INNER JOIN sys_citiao ct ON ct.bianhao = shen.citbh
INNER JOIN sys_jibzl zl ON zl.gonghao = shen.gonghao
WHERE shen.id = new.id;
if @fenshu > 0 then
set @jiafen = @fenshu;
set @jianfen = 0;
else
set @jiafen = 0;
set @jianfen = @fenshu;
end if;
INSERT INTO sys_mingxi(`kid`,`gonghao`,`vuid`,`zhibiao`,`citiao`,`bumen`,`jiafen`,`jianfen`,`yue`,`ctime`)
VALUES(@kid,@gonghao,@vuid,@zhibiao,@citiao,@bumen,@jiafen,@jianfen,0,@ctime);
end if;
END;
到这触发器成功了。
最后总结如下：
1、trigger 中不允许返回select出来的结果集
2、欲想通过一个SELECT语句对多个变量赋值，请采用以下语句形式：SELECT id,name INTO @v1,@v2 FROM ...
3、select into给变量赋值的语法不允许返回多行
4、定义变量时用了@符号，下面引用时也要用上@符号