我要實現的功能是：在更新一個表時，從三個表中查詢記錄並插入到另外一個表中，下面是我寫觸發器的過程：
第一次寫的觸發器如下：
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;
生成上面觸發器時報錯：Not allowed to return a result set from a trigger；原因是trigger 中不允許返回select出來的結果集，所以 “select @kid:=jl.kid....”部分改變成另一種寫法，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;
此時還是會報錯：SQL 錯誤 [1327] [42000]: Undeclared variable: shen; Undeclared variable: shen;原因是“select jl.skic into @kid...”部分的select語句的語法還是不對。
原因是：欲想通過一個SELECT語句對多個變量賦值，請採用以下語句形式：SELECT id,name INTO @v1,@v2 FROM ...
所以最終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;
到這運行的時候還是會報錯：ERROR 1172 (42000): Result consisted of more than one row；
這個報錯的原因是select into返回了多行記錄，這在給變量賦值的時候是不允許的，後來檢查是where條件的問題；
修改了where條件後返回一條記錄這個問題解決了。
再次運行時又報錯：SQL 錯誤 [1054] [42S22]: Unknown column 'fenshu' in 'field list' ；這個錯誤的原因是下面在引用變量“fenshu”時語法錯誤；
上面定義變量時用了@符號，下面引用時也要用上@符號。
最後觸發器改成如下：
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;
到這觸發器成功了。
最後總結如下：
1、trigger 中不允許返回select出來的結果集
2、欲想通過一個SELECT語句對多個變量賦值，請採用以下語句形式：SELECT id,name INTO @v1,@v2 FROM ...
3、select into給變量賦值的語法不允許返回多行
4、定義變量時用了@符號，下面引用時也要用上@符號