连接查询
内连接
select suppliers.s_id,s_name,f_name,f_price
from suppliers,fruits
where suppliers.s_id = fruits.s_id上述查询等价于inner join on 内连接查询
select suppliers.s_id,s_name,f_name,f_price
from suppliers inner join fruits
on suppliers.s_id = fruits.s_id对表名简写别名 再进行连接查询
select s1.s_id,s_name,f_name,f_price
from suppliers as s1 ,fruits
where s1.s_id = fruits.s_id外连接
左连接(返回左表所有数据和右表连接字段相等的数据)
右连接(返回右表所有数据和左表连接字段相等的数据)
left join on(左连接):
select customers.c_id,orders.o_nums
from customers left outer join orders
on customers.c_id = orders.c_idright join on(右连接):
select customers.c_id ,orders.o_nums
from customers right outer join orders
on customers.c_id = orders.c_id合并查询
select s_id ,f_name,f_price
from fruits
where f_price < 9.0
union all
select s_id,f_name,f_price
from fruits
where s_id in(101,103)分别给表和字段取别名进行查询
select f1.f_name as fruit_name,f1.f_price as fruit_price
from fruits as f1
where f1.f_price >1正则表达式查询
插入 更新 删除数据
插入(写法1)
insert into person(name,age,info)
values(
'Willam','20','sport man'
)插入(写法2)
insert into person
values(
'Willam','20','sport man'
)插入多条
insert into person
values(
'Willam','20','sport man'
),(
'Willam','20','sport man'
),(
'Willam','20','sport man'
),(
'Willam','20','sport man'
)将查询数据插入到表中
insert into person(id,name,age,info)
select id,name,age,info
from person_old更新数据
update person
set id='7' ,name='zzs',age='23',info='boss'
where id=1update person
set info='student '
where age between 19 and 22删除数据
delete from person
where id = '2'觉得有用的朋友点个赞,加个关注哦