1.查询整体表格数据
select * from car
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2.查询制定列
select code,price from car #code 代号 # price 价格 # car 表名
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3.给列指定名称
select code as'代号',name as'车名'from car
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4 条件查询
①单条件查询
select * from car where code ='c002'
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②多条件查询(用or或and链接)
select * from car where code='c002'or price='37.16'
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select * from car where code='c002' and price='67.49'
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5 模糊查询(关键字查询)
%关键字，关键字前面有n个字符；关键字%，关键字后面有n个字符,%符号代表n个字符
_关键字，关键字前面有一个字符；关键字_，关键字后面有一个字符,_符号代表一个字符
select * from car where name like '奥迪%'
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6 排序查询
select * from car order by price desc
根据价格降序排列
select *from car order by price desc, oil desc
先根据price降序排列，有重复的 在根据oil降序排列
desc降序 asc升序。 默认为升序
7去重查询
distinct去重
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8 分页查询
select * from car limit 5, 5 #去掉前五条,查询后5条, 当前页-1乘以5
9 统计查询(聚合函数)
select count(*) from car
select count(code) from car
select max(列名) from 表名 #取最大值 select min（列名） from 表名#取最小值 select avg （列名）from 表名#取平均值
10 分组查询
查询所有
select * from car group by brand
select brand ,count(*)from car group by brand
select brand from car group by brand having count(*)>=3 #有having前面必须有group by
#有group by 后面可以没有having
11范围查询 in 和 not in 相反 一个是是这些数的 一个是不是这些数的
select * from car where price between 40 and 60
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12 离散查询
select * from car where price in (10,20,30,40,50,60)
select * from car where price not in (10,20,30,40,50,60)
