Example analysis of while, repeat and loop loops in MySQL process control

MySQL Process control while、repeat、loop Cycle example analysis

Today I'd like to share with you MySQL Process control while、repeat、loop Relevant knowledge points of circular example analysis , Detailed content , Clear logic , I believe most people still know too much about this knowledge , So share this article for your reference , I hope you will gain something after reading this article , Now let's take a look .

Preface

• A loop is a segment that appears only once in a program , However, code may run multiple times in a row .

• The code in the loop runs a certain number of times , Or run to the end of the loop when certain conditions are established .

Cycle classification ：

• while

• repeat

• loop

Cycle control ：

leave Be similar to break, Jump out of , End the current cycle

iterate Be similar to continue, continue , End this cycle , Go on for the next time

while loop

【 label :】while  The loop condition  do The loop body ;end while【  label 】;

--  Create test table create table user (uid int primary_key,username varchar ( 50 ),password varchar ( 50 ));

-- ------- stored procedure -whiledelimiter $$create procedure proc16_while1(in insertcount int)begindeclare i int default 1;label:while i<=insertcount doinsert into user(uid,username,`password`) values(i,concat('user-',i),'123456');set i=i+1;end while label;end $$delimiter ;call proc16_while(10);

Stored procedure syntax is fixed ：delimiter $$ create peocedure Circular name （ Parameters ）begin Code end $$ delimiter;

Note that when writing the loop body , You must know the variables of the loop , use declare i int default The default value is

Then is dlabel：while Judge the condition do The loop body end while label; end && There must be

-- ------- stored procedure -while + leavetruncate table user;delimiter $$create procedure proc16_while2(in insertcount int)begindeclare i int default 1;label:while i<=insertcount doinsert into user(uid,username,`password`) values(i,concat('user-',i),'123456');if i=5 then leave label;end if;set i=i+1;end while label;end $$delimiter ;call proc16_while2(10);

If you need to jump out of the loop internally , use if Judge , But at the end of the day end if ending

there leave Namely Out of the loop , be relative to break

-- ------- stored procedure -while+iteratetruncate table user;delimiter $$create procedure proc16_while3(in insertcount int)begindeclare i int default 1;label:while i<=insertcount doset i=i+1;if i=5 then iterate label;end if;insert into user(uid,username,`password`) values(i,concat('user-',i),'123456');end while label;end $$delimiter ;call proc16_while3(10);

there iterate be relative to continue Do not execute the following code when encountering

repeat loop

repeat The loop body ;until  Conditional expression end repeat [ label ];

-- ------- stored procedure - Cycle control -repeatuse mysql7_procedure;truncate table user;delimiter $$create procedure proc18_repeat(in insertCount int)begindeclare i int default 1;label:repeatinsert into user(uid, username, password) values(i,concat('user-',i),'123456');set i = i + 1;until i > insertCountend repeat label;select ' The loop ends ';end $$delimiter ;call proc18_repeat(100);

This is relative to , In any case, the loop will be executed once , Then make internal judgment , If you are satisfied, just jump out

loop loop

 loop The loop body ;if  Conditional expression  thenleave [ label ];end if;end loop;

-- ------- stored procedure - Cycle control -looptruncate table user;delimiter $$create procedure proc19_loop(in insertCount int)begindeclare i int default 1;label:loopinsert into user(uid, username, password) values(i,concat('user-',i),'123456');set i = i + 1;if i > 5thenleave label;end if;end loop label;select ' The loop ends ';end $$delimiter ;call proc19_loop(10);

This and repeat The difference is , After execution , utilize leave Out of the loop , No matter which one is used, it can achieve the effect we need , But the application scenario in business ,while Still relatively more .

That's all “MySQL Process control while、repeat、loop Cycle example analysis ” All the content of this article , Thank you for reading ！ I believe you will gain a lot after reading this article , Xiaobian will update different knowledge for you every day , If you want to learn more , Please pay attention to the Yisu cloud industry information channel .