来自 新葡亰数据库 2019-11-24 00:42 的文章
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澳门新葡亰官网APP... END WHILE 复制代码 代码如下

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: WHILE ... END WHILE LOOP ... END LOOP REPEAT ... END REPEAT 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:GOTOWHILE ... END WHILE 复制代码 代码如下: CREATE PROCEDURE p14() BEGIN DECLARE v INT; SET v = 0; WHILE v < 5 DO INSERT INTO t VALUES ; 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。 REPEAT ... END REPEAT 复制代码 代码如下: CREATE PROCEDURE p15 () BEGIN DECLARE v INT; SET v = 0; REPEAT INSERT INTO t VALUES ; SET v = v + 1; UNTIL v >= 5 END 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。 LOOP ... END LOOP 复制代码 代码如下: CREATE PROCEDURE p16 () BEGIN DECLARE v INT; SET v = 0; loop_label: LOOP INSERT INTO t VALUES ; SET v = v + 1; IF v >= 5 THEN LEAVE 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语句的话,就必须用到LEAVE语句 复制代码 代码如下: CREATE PROCEDURE p20 () BEGIN DECLARE v INT; SET v = 0; loop_label: LOOP IF v = 3 THEN SET v = v + 1; ITERATE loop_label; END IF; INSERT INTO t VALUES ; SET v = v + 1; IF v >= 5 THEN LEAVE loop_label; END IF; END LOOP; END; ITERATE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: begin declare p_feeCode varchar; declare p_feeName varchar; declare p_billMoney float; declare p_schemeMoney float; declare allMoney float; declare allUsedMoney float; declare p_year varchar; declare p_totalCompeleteRate float; declare done int; declare flag int; 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 into p_year; open feeCodeCursor;//打开游标 loop_label:LOOP fetch feeCodeCursor into p_feeCode;//将游标插入申明的变量 if done = 1 then leave loop_label; else set 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 into p_billMoney from bill_data where feeCode=p_feeCode and billDate like Concat; select schemeMoney into p_schemeMoney from total_scheme where feeCode=p_feeCode and schemeDate like Concat limit 1; if flag = 0 then set done = 0; end if; if p_schemeMoney=0 then set p_totalCompeleteRate=-1.0; else set p_totalCompeleteRate=/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: begin declare p_projectID varchar; declare p_projectName varchar; declare p_feeCode varchar; declare p_feeName varchar; declare p_projectSchemeMoney float; declare p_projectMoney float; declare p_billMoney float; declare p_year varchar; declare p_projectFeeCompeleteRate float; declare done1 int; declare done2 int; declare flag int; declare feeCodeCursor cursor for select feeCode from fee; declare continue handler for not found set done1=1; set done1=0; select date_format 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 then begin declare 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 then leave loop_label; else set flag = 0; end if; if not done2 then set p_projectSchemeMoney=0; select sum into p_billMoney from bill_data where feeCode=p_feeCode and projectID=p_projectID and billDate like Concat; select projectSchemeMoney into p_projectSchemeMoney from project_scheme where feeCode=p_feeCode and projectID=p_projectID; if flag = 0 then set done2 = 0; end if; if p_projectSchemeMoney=0 then set p_projectFeeCompeleteRate=-1; else set p_projectFeeCompeleteRate=/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 into p_projectMoney from bill_data where feeCode=p_feeCode and billDate like Concat; set p_projectFeeCompeleteRate=/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 done1 end repeat; close feeCodeCursor; end

本文由澳门新葡亰app发布于新葡亰数据库,转载请注明出处:澳门新葡亰官网APP... END WHILE 复制代码 代码如下

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