SQL学习笔记八索引，表连接，子查询，ROW_NUMBER

索引

经常要查询的语句，则给它建一个索引

 

表连接

select T_Oders as o join T_Customers as C on o.CustomerId = c.Id

 

子查询

单值子查询

单列多值子查询

 

ROW_NUMBER()函数

ROW_NUMBER() OVER(ORDER BY Fsalary DESC)