T-SQL语句：
创建表：create table name( code varchar(50),)
主键：primary key
非空：not null
自增长：auto_increment
外键：references
删除表： drop table family
创建数据库：create database mydb
删除数据库：drop database mydb
CRUD操作：
C: create
增加数据：
insert into nation values（'n001','汉族'）--普通添加
insert into nation values('','','') -- 自增长列也要添加
insert into nation (code) values ('n002')--往表中添加特定列的数据
R: read
查询数据：
1、查询所有数据 select * from info
查特定列 select code,name from info
2、根据条件差
select * from info where code='p001' 一个条件查询
select * from info where code='p001' and nation ='n001' 多条件 并关系 查询
select * from info where code='p001' or nation = 'n001' 多条件 或关系
select * from car where price>=50 and price <= 60 范围查询
select * from car where price between 50 and 60
3、模糊查询
select * from car where name like '%型' 已型为结束的数据 ------》 %通配符代表任意多个字符
select * from car where name like'%奥迪%'
select * from car where name like'_马%'
4、排序
select * from car order by price asc 按照价格升序排列(默认)asc 可以省去不写
select * from car order by price desc 按照价格降序排列
select * from car order by price desc ,oil desc 按照两列进行排序 前面的为主要
5、统计函数（聚合函数）
select count(code) from car 查询表中有多少条数据
select max(price) from car 取价格中最大值
select min(price) from car 取价格最小值
select sum(price) from car 取价格的总和
select avg(price) from car 取价格的平均值
6、分组查询
select * from car group by brand
select brand from car group by brand
select count(brand) from car group by brand 获取分组每组的数量
select brand from car group by brand having count(*)>2 分组后筛选数量大于2的
7、分页查询
select * from car limit m,n 跳过m条数据去n条数据
8、去重查询
select distinct brand from car
U：update
修改数据：
update nation set name = '回族' ---全部修改
update nation set name = ‘汉族’ where code = 'n002' --修改某一条数据
update nation set code = 'n003' where name = '汉族'
D：delete
删除数据：
delete from nation--删除整个表中的数据
delete from nation where code = 'n001' 删除一条数据，已主键查询删除一条，如果以别的数据查询可能删除多条--重名。