每种类型记录的SQL Server示例

Question

我有一个包含各个学期记录的表格,我想要一个查询来选择每个学期的前5行.

我想要一个按键字段(序列)排序的结果集和一个在每个学期内随机排序的结果集.

该表如下所示:

• 串行整数
• 学期char(4)
• 等级int

表数据:

Semester|Serial|NewSerial
SP10    |1     |1001
SP10    |2     |1002
SP10    |3     |1003
SP10    |4     |1004
SP10    |5     |1005
SP10    |6     |1006
SP10    |7     |1007
SP10    |8     |1008
SP10    |9     |1009
SP10    |10    |1010
FA10    |1     |2001
FA10    |2     |2002
FA10    |3     |2003
FA10    |4     |2004
FA10    |5     |2005
FA10    |6     |2006
FA10    |7     |2007
FA10    |8     |2008
FA10    |9     |2009
FA10    |10    |2010
FA09    |1     |3001
FA09    |2     |3002
FA09    |3     |3003
FA09    |4     |3004
FA09    |5     |3005
FA09    |6     |3006
FA09    |7     |3007
FA09    |8     |3008
FA09    |9     |3009
FA09    |10    |3010

结果1:按序列排序,前5名

Semester|Serial|NewSerial
SP10    |1     |1001
SP10    |2     |1002
SP10    |3     |1003
SP10    |4     |1004
SP10    |5     |1005
FA10    |1     |2001
FA10    |2     |2002
FA10    |3     |2003
FA10    |4     |2004
FA10    |5     |2005
FA09    |1     |3001
FA09    |2     |3002
FA09    |3     |3003
FA09    |4     |3004
FA09    |5     |3005

结果2:学期内随机排序(抽样)

Semester|Serial|NewSerial
SP10    |3     |1003
SP10    |1     |1001
SP10    |5     |1005
SP10    |2     |1002
SP10    |4     |1004
FA10    |2     |2002
FA10    |1     |2001
FA10    |4     |2004
FA10    |3     |2003
FA10    |5     |2005
FA09    |3     |3003
FA09    |1     |3001
FA09    |2     |3002
FA09    |5     |3005
FA09    |4     |3004

Answer 1

这些应该这样做:

WITH [query_semester] AS (
    SELECT RN = ROW_NUMBER() OVER (PARTITION BY semester
    ORDER BY serial),
    serial, semester, grade
    FROM SemesterTable)
SELECT serial, semester, grade
FROM [query_semester] WHERE [RN] <= 5;

和随机的:

WITH [query_semester] AS (
    SELECT RN = ROW_NUMBER() OVER (PARTITION BY semester
    ORDER BY NEWID()),
    serial, semester, grade
    FROM SemesterTable)
SELECT serial, semester, grade
FROM [query_semester] WHERE [RN] <= 5;