求指教mysql的delete怎么和子循环使用?

DELETE from sc where score in(
SELECT score from sc WHERE cno in (SELECT cno from course
where tno in (SELECT tno from teacher
where tname = "李老师"
)
) as a)

小怪兽爱吃肉
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2回答

慕桂英4014372

DELETE FROM SC USING SC,Course,TeacherWHERE sc.cno=course.cno and course.tno=teacher.tnoand teacher.tname='李老师'

PIPIONE

Mysql的存储过程是从版本5才开始支持的,所以目前一般使用的都可以用到存储过程。今天分享下自己对于Mysql存储过程的认识与了解。一些简单的调用以及语法规则这里就不在赘述,网上有许多例子。这里主要说说大家常用的游标加循环的嵌套使用。首先先介绍循环的分类:(1)WHILE ... END WHILE(2)LOOP ... END LOOP(3)REPEAT ... END REPEAT(4)GOTO这里有三种标准的循环方式:WHILE循环,LOOP循环以及REPEAT循环。还有一种非标准的循环方式:GOTO(不做介绍)。(1)WHILE ... END WHILE复制代码 代码如下:CREATE PROCEDURE p14()BEGINDECLARE v INT;SET v = 0;WHILE v < 5 DOINSERT INTO t VALUES (v);SET v = v + 1;END WHILE;END;这是WHILE循环的方式。它跟IF语句相似,使用"SET v = 0;"语句使为了防止一个常见的错误,如果没有初始化,默认变量值为NULL,而NULL和任何值操作结果都为NULL。(2)REPEAT ... END REPEAT复制代码 代码如下:CREATE PROCEDURE p15 ()BEGINDECLARE v INT;SET v = 0;REPEATINSERT INTO t VALUES (v);SET v = v + 1;UNTIL v >= 5END REPEAT;END;这是REPEAT循环的例子,功能和前面WHILE循环一样。区别在于它在执行后检查结果,而WHILE则是执行前检查。类似于do while语句。注意到UNTIL语句后面没有分号,在这里可以不写分号,当然你加上额外的分号更好。(3)LOOP ... END LOOP复制代码 代码如下:CREATE PROCEDURE p16 ()BEGINDECLARE v INT;SET v = 0;loop_label: LOOPINSERT INTO t VALUES (v);SET v = v + 1;IF v >= 5 THENLEAVE loop_label;END IF;END LOOP;END;以上是LOOP循环的例子。LOOP循环不需要初始条件,这点和WHILE循环相似,同时它又和REPEAT循环一样也不需要结束条件。ITERATE 迭代如果目标是ITERATE(迭代)语句的话,就必须用到LEAVE语句复制代码 代码如下:CREATE PROCEDURE p20 ()BEGINDECLARE v INT;SET v = 0;loop_label: LOOPIF v = 3 THENSET v = v + 1;ITERATE loop_label;END IF;INSERT INTO t VALUES (v);SET v = v + 1;IF v >= 5 THENLEAVE loop_label;END IF;END LOOP;END;ITERATE(迭代)语句和LEAVE语句一样也是在循环内部的循环引用, 它有点像C语言中 的“Continue”,同样它可以出现在复合语句中,引用复合语句标号,ITERATE(迭代)意思 是重新开始复合语句。以上是对于循环的几种情况的介绍。接着就是介绍一个带游标的例子来详细解释。复制代码 代码如下:begindeclare p_feeCode varchar(20);declare p_feeName varchar(20);declare p_billMoney float(12);declare p_schemeMoney float(12);declare allMoney float(10);declare allUsedMoney float(10);declare p_year varchar(50);declare p_totalCompeleteRate float(12);declare done int(10);declare flag int(2);declare feeCodeCursor cursor for select feeCode from fee;//申明一个游标变量declare continue handler for not found set done=1;//申明循环结束的标志位set done=0;select date_format(now(),'%Y') into p_year;open feeCodeCursor;//打开游标loop_label:LOOPfetch feeCodeCursor into p_feeCode;//将游标插入申明的变量if done = 1 thenleave loop_label;elseset flag = 0;end if;set p_schemeMoney=0;set p_billMoney = 0;select feeName into p_feeName from fee where feeCode=p_feeCode;select sum(billMoney) into p_billMoney from bill_data where feeCode=p_feeCode and billDate like Concat(p_year, '%');select schemeMoney into p_schemeMoney from total_scheme where feeCode=p_feeCode and schemeDate like Concat(p_year, '%') limit 1;if flag = 0 thenset done = 0;end if;if p_schemeMoney=0 thenset p_totalCompeleteRate=-1.0;elseset p_totalCompeleteRate=(1.0*p_billMoney)/p_schemeMoney;end if;insert into total_summary values(p_feeCode,p_feeName,p_year,p_billMoney,p_totalCompeleteRate);commit;end LOOP;close feeCodeCursor;//循环结束后需要关闭游标end以上只是一个简单的例子来说明如何使用,大家不需要关注具体业务逻辑,只需要关注的是其中标志位值的修改情况,已经循环何时离开。以及游标如何声明,如何使用,至于里面具体的操作和普通的sql语句没有太大区别。此处是用一层循环,至于复杂业务需要需要两层三层,可以继续用同样的方法继续嵌套。以下给出双层嵌套循环的,同样大家只需要关注嵌套结构即可。复制代码 代码如下:begindeclare p_projectID varchar(20);declare p_projectName varchar(20);declare p_feeCode varchar(20);declare p_feeName varchar(20);declare p_projectSchemeMoney float(10);declare p_projectMoney float(10);declare p_billMoney float(10);declare p_year varchar(50);declare p_projectFeeCompeleteRate float(10);declare done1 int(10);declare done2 int(10);declare flag int(2);declare feeCodeCursor cursor for select feeCode from fee;declare continue handler for not found set done1=1;set done1=0;select date_format(now(),'%Y') into p_year;delete from project_fee_summary;open feeCodeCursor;repeat //第一层嵌套开始fetch feeCodeCursor into p_feeCode;select feeName into p_feeName from fee where feeCode=p_feeCode;if not done1 thenbegindeclare projectIDCursor cursor for select projectID from project;declare continue handler for not found set done2 = 1;set done2=0;open projectIDCursor;loop_label:LOOP//第二层嵌套开始fetch projectIDCursor into p_projectID;select projectName into p_projectName from project where projectID=p_projectID;if done2 = 1 thenleave loop_label;elseset flag = 0;end if;if not done2 thenset p_projectSchemeMoney=0;select sum(billMoney) into p_billMoney from bill_data where feeCode=p_feeCode and projectID=p_projectID and billDate like Concat(p_year, '%');select projectSchemeMoney into p_projectSchemeMoney from project_scheme where feeCode=p_feeCode and projectID=p_projectID;if flag = 0 thenset done2 = 0;end if;if p_projectSchemeMoney=0 thenset p_projectFeeCompeleteRate=-1;elseset p_projectFeeCompeleteRate=(1.0*p_billMoney)/p_projectSchemeMoney;end if;insert into project_fee_summary values(p_feeCode,p_projectID,p_projectName,p_feeName,p_year,p_billMoney,p_projectFeeCompeleteRate,p_projectFeeCompeleteRate);end if;end LOOP;select sum(billMoney) into p_projectMoney from bill_data where feeCode=p_feeCode and billDate like Concat(p_year, '%');set p_projectFeeCompeleteRate=(1.0*p_projectMoney)/p_projectSchemeMoney;insert into project_fee_summary values(p_feeCode,"total","total",p_feeName,p_year,p_projectMoney,p_projectFeeCompeleteRate,p_projectFeeCompeleteRate);close projectIDCursor;end;end if;until done1end repeat;close feeCodeCursor;end
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Java