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_id
right 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=1
update person
set info='student '
where age between 19 and 22
删除数据
delete from person
where id = '2'
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