mysql游标循环_mysql存储过程游标循环使⽤介绍
今天分享下⾃⼰对于Mysql存储过程的认识与了解，这⾥主要说说⼤家常⽤的游标加循环的嵌套使⽤
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
CREATE PROCEDURE p14()
BEGIN
DECLARE v INT;
SET v = 0;
WHILE v < 5 DO
INSERT 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
CREATE PROCEDURE p15 ()
BEGIN
DECLARE v INT;
SET v = 0;
REPEAT
INSERT INTO t VALUES (v);
SET v = v + 1;
UNTIL v >= 5
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
CREATE PROCEDURE p16 ()
BEGIN
DECLARE v INT;
SET v = 0;
loop_label: LOOP
INSERT INTO t VALUES (v);
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(迭代)语句的话，就必须⽤到LEAVE语句
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 (v);
SET v = v + 1;
IF v >= 5 THEN
LEAVE loop_label;
END IF;
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。
begin
declare 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: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(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 then
if p_schemeMoney=0 then
set p_totalCompeleteRate=-1.0;
else
set 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
mysql存储过程使用套。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。
begin
declare 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
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(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 then
set done2 = 0;
end if;
if p_projectSchemeMoney=0 then
set p_projectFeeCompeleteRate=-1;
else
set 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_projectFeeCompeleteRa
end if;
end LOOP;
select sum(billMoney) into p_projectMoney from bill_data where feeCode=p_feeCode and billDate like Concat(p_year, '%');

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