MySql练习、整理

use abccs;

select * from mytable2 limit 3,4;

call sp_name1(1,@nn);

select @nn;

select length('sdaf');

select sum(1) from mytable2 where mytable2.name='8';

select sum_hell('abv');

select * from t;

#描述表t结构

desc t;

#添加一列设置为主键

alter table t add id int,add primary key (id);

#删除列my_order

alter table t drop column my_order;--

alter table t add my_order char(1) default 'Y';

#修改表列类型

alter table t modify my_order varchar(10);

alter table t change my_order my_order char(1);

#修改表 列名address1 为id

alter table t change column address1 id int;

#删除存储过程testName

drop procedure testName;

delimiter //

create procedure testName(in name varchar(10),out para varchar(10))

begin

declare deName varchar(10);

#NOT FOUND,SQLEXCEPTION,SQLWARNING

declare continue handler for not found,sqlexception,sqlwarning set @sp2=10;#begin end;

set @sp1=1;

delete from t where id <10;

set @sp1=2;

insert into t values(2,3);

set @sp1=3;

insert into t values(2,3);

set @sp1=4;

select id into para from t;

end;

call testName(2,@a);

select @a, @sp1, @sp2;

//

delimiter //

create procedure testTration()

begin

declare continue handler for not found,sqlexception,sqlwarning rollback;

start transaction;

insert into t values(3,'Y');

insert into t values(4,'Y');

commit;

end;

call testTration();

#用户变量

set @cvar=23;

##系统变量

#全局系统变量

set global eee=234

#会话系统变量

set @@var

# 单行注释

-- 单行注释

/*

多行注释

eeee

*/