对标题感到抱歉 - 我很难简洁地说出来
所以我有一些数据当前都在一个表中,我希望将它存储在两个不同的表中。这是我的情况的简单版本:
Person:
+----+-----------+----------+----------+
| Id | FirstName | LastName | City |
+----+-----------+----------+----------+
| 1 | Billy | Bob | Toronto |
| 2 | Billy | Bob | Mumbai |
| 3 | Sally | Ann | Toronto |
| 4 | Joe | Hall | New York |
| 5 | Joe | Hall | Boston |
+----+-----------+----------+----------+
所以我有一群人和他们的城市。我想这样做,所以给定的名字/姓氏组合只出现一次,第二个表描述名称id< - >城市组合,如此:
Person:
+----+-----------+----------+
| Id | FirstName | LastName |
+----+-----------+----------+
| 1 | Billy | Bob |
| 3 | Sally | Ann |
| 4 | Joe | Hall |
+----+-----------+----------+
LivesIn:
+----------+----------+
| PersonId | City |
+----------+----------+
| 1 | Toronto |
| 1 | Mumbai |
| 3 | Toronto |
| 4 | New York |
| 4 | Boston |
+----------+----------+
我的问题是:如何只选择每个名称组合的第一个实例插入第二个表?为了准确地移动数据,我可以这样做:
INSERT INTO LivesIn (PersonId, City)
SELECT Id, City
FROM Person
但这意味着LivesIn
仍会有两个不同的PersonId
到同一个名称组合。
答案 0 :(得分:2)
INSERT INTO LivesIn (PersonId, City)
select t1.id, t2.City
from
(
SELECT min(Id) as id, FirstName, LastName
FROM Person
GROUP BY FirstName, LastName
) t1
join person t2 on t1.FirstName = t2.FirstName
and t1.LastName = t2.LastName