1.增加内容
insert into xuesheng values(‘5‘,‘赵六‘,‘1‘,‘16‘)
# insert into<表名>values(<‘值1‘>,<‘值2‘>,<‘值3‘>,<‘值4‘>)
insert into xuesheng (xuehao,xingming) values(‘6‘,‘朱八‘)
# insert into <表名>(<列1>，<列2>)values(<‘值1‘>,<‘值2‘>)
2.删除数据
delete from xuesheng where xuehao=‘8‘
# delete from <表名> where <列1>=<‘值1‘>
3.修改数据
update xuesheng set xingming=‘田七‘ where xuehao=‘6‘
# update <表名> set <列1>=<‘值1‘> where <列1>=<‘值1‘>
4.查询数据
(1)简单查询
select * from xuesheng
# select * from <表名>
select xuehao as‘学号‘,xingming as‘姓名‘ from xuesheng
# select <列1> as <‘中文‘>,<列2>as<‘中文‘> from <表名>
(2)条件查询
select * from car where code=‘c002‘
# select * from <表名> where <列1>=<‘值1‘>
select * from car where brand=‘b001‘ and powers=130
# select * from <表名> where <列1>=<‘值1‘> and <列2>=<‘值2‘>
select * from car where brand=‘b001‘ or powers=130
# select * from <表名> where <列1>=<‘值1‘> or <列2>=<‘值2‘>
(3)模糊查询
%代表任意多个字符 _代表一个字符
select * from car where name like ‘奥迪%‘
# select * from <表名> where <列1> like <‘值1%‘>
select * from car where name like ‘%型‘
# select * from <表名> where <列1> like <‘%型‘>
select * from car where name like ‘%舒适%‘
# select * from <表名> where <列1> like <‘%舒适%‘>
select * from car where name like ‘__A6L%‘
# select * from <表名> where <列1> like <‘__A6L%‘>
(4)排序查询
select * from car order by powers
# select * from <表名> order by <列名> 默认升序
select * from car order by powers desc
# select * from <表名> order by <列名> desc 降序
select * from Car order by Brand,Powers desc
# select * from <表名> order by <列1><列2> desc 多个列名查询
(5)范围查询
select * from car where price>=40 and price<=60
# select * from <表名> where <列名>>=<值1> and <列名><=<值2>
select * from car where price between 40 and 50
# select * from <表名> where <列名> between <值1> and <值2>
(6)离散查询
select * from car where code in (‘c001‘,‘c005‘,‘c008‘)
# select * from <表名> where <列名> in (<‘值1‘>,<‘值2‘>,<‘值3‘>)
select * from car where code not in (‘c001‘,‘c005‘,‘c008‘)
# select * from <表名> where <列名> not in (<‘值1‘>,<‘值2‘>,<‘值3‘>)
(7)聚合函数：统计查询
select sum(price) from car
# select sum(<列名>)from <表名>
# 查询所有价格之和 sum() 求和
select count(price) from car
# select count(<列名>) from <表名>
# 查询数据条数
select max(code) from car
# select max(<列名>) from <表名>
# 求最大值
select min(code) from car
# select min(<列名>) from <表名>
# 求最小值
select avg(price) from car
# select avg(<列名>) from <表名>
# 求平均值
(8)分页查询
select * from Car limit 10,5
# select * from <表名> limit (n-1)*5,5
# 每页显示5条数据，取第2页的数据
(9)去重查询
select distinct brand from car
# select distinct <列名> from <表名>
(10)分组查询
select count(*),brand from car group by brand
# select count(<所有全部>),<列名> from <表名> group by <列名>
select brand from car group by brand having count(*)>1
# select <列名> from <表名> group by <列名> having count(<所有全部>)>1
# 分组之后根据条件查询使用having 不使用where