簡單查詢：
1.最簡單查詢（查所有數據）
select * from 表名； 注：* 代表所有列
select * from info
2.查詢指定列
select code,name from info
3.修改結果集的列名
select code as '代號',name as '姓名' from info
4.條件查詢
select * from info where code='p003'
5.多條件查詢
查詢info表中code為p003或者nation為n001的所有數據
select * from info where code='p003' or nation='n001'
查詢info表中code為p004並且nation為n001的數據
select * from info where code='p004' and nation='n001'
6.范圍查詢
select * from car where price>=40 and price<=60
select * from car where price between 40 and 60
7.離散查詢
查詢汽車價格在（10,20,30,40,50,60）中出現的汽車信息
select * from car where price=10 or price=20 or price=30 or price=40 or price=50 or price=60
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)
8.模糊查詢（關鍵字查詢）
查詢car表里面名稱包含奧迪的
select * from car where name like '%奧迪%' %任意n個字符
查詢car中名稱第二個字符為‘馬’的汽車
select * from car where name like '_馬%' _任意一個字符
9.排序查詢
select * from car order by price asc asc升序（省略）
select * from car order by oil desc desc降序
先按照brand升序排，再按照price降序排
select * from car order by brand,price desc
10.去重查詢
select distinct brand from car
11.分頁查詢
一頁顯示10條 當前是第3頁
select * from chinastates limit 20,10
一頁顯示m條 當前是第n頁
limit (n-1)*m，m
12.聚合函數（統計函數）
select count(areacode) from chinastates #查詢數據總條數
select sum(price) from car #求和
select avg(price) from car #求平均
select max(price) from car #求最大值
select min(price) from car #求最小值
13.分組查詢
查詢汽車表中每個系列下有多少個汽車
select brand,count(*) from car group by brand
查詢汽車表中賣的汽車數量大於1的系列
select brand from car group by brand having count(*)>1
