SQL语句

Question

如果我有下表：

CREATE TABLE #temp (
    id int,
    num int,
    question varchar(50),
    qversion int );

INSERT INTO #temp VALUES(1, 1, 'Question 1 v1', 1);
INSERT INTO #temp VALUES(2, 1, 'Question 1 v2', 2);
INSERT INTO #temp VALUES(3, 2, 'Question 2 v1', 1);
INSERT INTO #temp VALUES(4, 2, 'Question 2 v2', 2);
INSERT INTO #temp VALUES(5, 2, 'Question 2 v3', 3);
INSERT INTO #temp VALUES(6, 3, 'Question 3 v1', 1);

SELECT *
FROM #temp;

DROP TABLE #temp;

我想要一个表格来显示这三个问题的最新版本？这是在SQL Server 2005中

Answer 1

CREATE TABLE #temp (
    id int,
    num int,
    question varchar(50),
    qversion int );

INSERT INTO #temp VALUES(1, 1, 'Question 1 v1', 1);
INSERT INTO #temp VALUES(2, 1, 'Question 1 v2', 2);
INSERT INTO #temp VALUES(3, 2, 'Question 2 v1', 1);
INSERT INTO #temp VALUES(4, 2, 'Question 2 v2', 2);
INSERT INTO #temp VALUES(5, 2, 'Question 2 v3', 3);
INSERT INTO #temp VALUES(6, 3, 'Question 3 v1', 1);

WITH latest AS (
   SELECT num, MAX(qversion) AS qversion
   FROM #temp
   GROUP BY num
)
SELECT #temp.*
FROM #temp
INNER JOIN latest
    ON latest.num = #temp.num
    AND latest.qversion = #temp.qversion;

DROP TABLE #temp;

Answer 2

SELECT t1.id, t1.num, t1.question, t1.qversion
FROM #temp t1
LEFT OUTER JOIN #temp t2
  ON (t1.num = t2.num AND t1.qversion < t2.qversion)
GROUP BY t1.id, t1.num, t1.question, t1.qversion
HAVING COUNT(*) < 3;

Answer 3

您使用的是SQL Server2005，因此至少值得研究一下over子句：

select
    *
from
    (select *, max(qversion) over (partition by num) as maxVersion from #temp) s
where
    s.qversion = s.maxVersion