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
①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'
or:或的關系。
查詢info表中code為p004並且nation為n001的數據
②select * from info where code='p004' and nation='n001'
and:和的關系。
6、范圍查詢
between:在某某之間。
復雜寫法:select*from car where price>=40 and price<=60
簡單寫法: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。
in():在括弧里出現的。
not in():不在括弧里出現的。
復雜寫法:select * from car where praice=10 praice=20 praice=30 praice=40 praice=50 praice=60
簡單寫法: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)like
like:名稱前面加。
%:任意多個字符。
_下划線 任意一個字符。
①查詢汽車表里面名稱包含奧迪的。
select * from car where name like '%奧迪%'
②查詢汽車表中名稱第二個字符為‘馬’的汽車
select * from car where name like '_馬%'
9、排序查詢
asc:升序(可省略)
desc: 降序
order by: 排序
①升序排序:select * from car order by price asc
先按照brand升序排,再按照price降序排。
②降序排序:select * from car order by brand,price desc
10、去重查詢
select distinct brand from car
11、分頁查詢
一頁顯示十條,當前是第二頁。
linmit:分頁
select * from chainastates limit 10(跳過的數據),10(取多少條)
如果一頁顯示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
①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
②查詢汽車表中賣的汽車數量大於3的系列
select brand from car group by brand having count(*)>3