1.查詢一張表(orders)的所以紀錄

  select   *   from  Orders

2.查詢一張表(orders)某字段的所有記錄

  select  OrderID,OrderDate from Orders

如需有條件地從表中選取數據，可將 WHERE 子句添加到 SELECT 語句

  select  * from Orders where OrderID=10004

分組查詢，根據某些字段進行分組查詢，查詢返回的字段只能是跟在grooup by后面的分組字段

select   *   from  Orders  group by OrderID    錯誤select   OrderID   from Orders  group by OrderID    正確//當根據多個字段進行分組時,從左到右進行一步一步分組 select OrderDate, CustomerID from Orders group by OrderDate,CustomerID

having的作用和where一樣是條件篩選，但是having是對分組后的集合進行篩選，和Group by一起使用

select   OrderID from Orders   group by OrderID having OrderID=10004

order by 語句用于對結果集進行排序 order by column asc/desc //asc--升序(默認), desc--降序

select   OrderID from Orders   order by OrderID     //按OrderID進行升序排列select   OrderID from Orders   order by OrderID asc  //按OrderID進行升序排列select   OrderID from Orders   order by OrderID desc  //按OrderID進行降序排列

TOP 子句用于規定要返回的記錄的數目

select top 10 OrderID from Orders   //返回前10條記錄select top 10 percent OrderID from Orders   //返回前百分之10的紀錄

from -> where -> group by -> having -> select -> order by -> top

select top 1 OrderID from Orders where OrderID=10004         　　　　 group by OrderID having OrderID=10004 order by OrderID