Question

我有以下查询：

SELECT distinct person, address, from_date, to_date 
  FROM db
 WHERE '2000-01-01' BETWEEN from_date AND to_date

这很好，但是它在2000年1月1日带回了一些有多个地址的人。我想只选择具有最大to_date的地址。

即查询返回：

person-------------address--------from_date--------to_date
1------------------34-------------1999-06-12-------2000-04-04 
1------------------27-------------1999-06-12-------2000-12-12

我想只选择第二行。

以下是否足够？

SELECT distinct person, address,from_date, MAX(to_date) 
  FROM db
WHERE '2000-01-01' BETWEEN from_date AND to_date

Answer 1

查询可能类似（但可以进一步简化）：

SELECT db.person, address, from_date,db.to_date
  FROM db, (SELECT person, max(to_date) to_date
            FROM db
           GROUP BY person) db_max
WHERE '2000-01-01' BETWEEN db.from_date AND db.to_date
  AND db.to_date = db_max.to_date
  AND db.person = db_max.person;

Answer 2

SELECT person, address,from_date, to_date
  FROM db db_outer
 WHERE '2000-01-01' BETWEEN from_date AND to_date
   AND EXISTS (SELECT 1
                 FROM db db_inner
                WHERE db_outer.person = db_inner.person
             GROUP BY db_inner.person
               HAVING MAX(db_inner.to_date) = db_outer.to_date)

Answer 3

你需要一个子查询：http://allenbrowne.com/subquery-01.html是最好的解释，子查询可以有一个订单，因为你有一个“顶部”

选择最好的约会

3 个答案: