SQL语句数据行操作补充
create table tb12(
id int auto_increment primary key,
name varchar(32),
age int
)engine=innodb default charset=utf8;
增
insert into tb11(name,age) values('alex',12);
insert into tb11(name,age) values('alex',12),('root',18); #同时增加多条
insert into tb12(name,age) select name,age from tb11; #将tb11表整个插入tb12
删
delete from tb12;
delete from tb12 where id !=2
delete from tb12 where id =2
delete from tb12 where id > 2
delete from tb12 where id >=2
delete from tb12 where id >=2 or name='alex'
改
update tb12 set name='alex' where id>12 and name='xx' #条件
update tb12 set name='alex',age=19 where id>12 and name='xx'
查
select * from tb12;
select id,name from tb12;
select id,name from tb12 where id > 10 or name ='xxx';
select id,name as cname from tb12 where id > 10 or name ='xxx'; #将name取别名显示
select name,age,11 from tb12; #第三列全为11
其他：
select * from tb12 where id != 1
select * from tb12 where id in (1,5,12); # 1 or 5 or 12
select * from tb12 where id not in (1,5,12);
select * from tb12 where id in (select id from tb11) #范围克重另一张表中选择
select * from tb12 where id between 5 and 12; #闭区间
通配符：
select * from tb12 where name like "a%" #以a开头的 %a以a结尾的
select * from tb12 where name like "a_" #a后边只有一个位置
分页：
select * from tb12 limit 10; #分页显示
select * from tb12 limit 0,10;
select * from tb12 limit 10,10;
select * from tb12 limit 20,10; #起始位置，和显示数量 从20个开始，往后显示10个
select * from tb12 limit 10 offset 20;
从第20行开始读取，读取10行；
排序：
select * from tb12 order by id desc; 大到小
select * from tb12 order by id asc; 小到大
select * from tb12 order by age desc,id desc;
取后10条数据 id从大到小排后取前十个
select * from tb12 order by id desc limit 10;
补充：
左右连表： join
上下连表： union
# 自动去重
select id,name from tb1
union
select num,sname from tb2
# 不去重
select sid,sname from student
UNION ALL
select sid,sname from student
