我有两张表格如下
Table 1 ----------------------------------- UserID | UserName | Age | Salary ----------------------------------- 1 | foo | 22 | 33000 -----------------------------------
Table 2 ------------------------------------------------ UserID | Age | Salary | CreatedDate ------------------------------------------------ 1 | NULL | 35000 | 2015-01-01 ------------------------------------------------ 1 | 28 | NULL | 2015-02-01 ------------------------------------------------ 1 | NULL | 28000 | 2015-03-01 ------------------------------------------------
我需要这样的结果。
Result ----------------------------------- UserID | UserName | Age | Salary ----------------------------------- 1 | foo | 28 | 28000 -----------------------------------
这只是一个例子。在我的真实项目中,我在上表中有大约6列,如Age和Salary。
在表2中,每条记录只有一个值,如果Age有值,则Salary将为NULL,反之亦然。
更新:
表2包含CreatedDate列。所以我想得到最新的" NOTNULL" CELL值而不是最大值。
答案 0 :(得分:4)
您可以使用简单的MAX()
和GROUP BY
:
select t1.userid,t1.username, MAX(t2.Age) as Age, MAX(t2.Salary) as Salary
from table1 t1 join
table2 t2 on t1.userid=t2.userid
group by t1.userid,t1.username
结果:
userid username Age Salary
--------------------------------
1 foo 28 35000
中的示例结果
答案 1 :(得分:3)
注意:我怀疑您知道自己在做什么,而且您还没有告诉我们您的架构的所有信息。
看起来Table 2
实际上是"更新"表,其中每行包含要应用于Table 1
中的基本实体的更改增量。在这种情况下,您可以使用相关联接(技术上是外部应用)检索每个列的数据并将结果放在一起。如下所示:
select a.UserID, a.UserName,
coalesce(aAge.Age, a.Age),
coalesce(aSalary.Salary, a.Salary)
from [Table 1] a
outer apply (
select Age
from [Table 2] x
where x.UserID = a.UserID
and x.Age is not null
and not exists (
select 1
from [Table 2] y
where x.UserID = y.UserID
and y.Id > x.Id
and y.Age is not null
)
) aAge,
outer apply (
select Salary
from [Table 2] x
where x.UserID = a.UserID
and x.Salary is not null
and not exists (
select 1
from [Table 2] y
where x.UserID = y.UserID
and y.Id > x.Id
and y.Salary is not null
)
) aSalary
请注意我假设您Id
中至少有一个Table 2
列,每个插入都会单调增加。如果你有'#34;更改时间"列,使用它来获取最新的行,因为它更好。
答案 2 :(得分:2)
要根据CreatedDate
获取最新值,您可以使用ROW_NUMBER
过滤最新行。此处的分区基于UserID
,其他列Age
和Salary
。
;WITH Cte AS(
SELECT
UserID,
Age = MAX(Age),
Salary = MAX(Salary)
FROM(
SELECT *, Rn = ROW_NUMBER() OVER(
PARTITION BY
UserID,
CASE
WHEN Age IS NOT NULL THEN 1
WHEN Salary IS NOT NULL THEN 2
END
ORDER BY CreatedDate DESC
)
FROM Table2
)t
WHERE Rn = 1
GROUP BY UserID
)
SELECT
t.UserID,
t.UserName,
Age = ISNULL(c.Age, t.Age),
Salary = ISNULL(c.Salary, t.Salary)
FROM Table1 t
LEFT JOIN Cte c
ON t.UserID = c.UserID
答案 3 :(得分:0)
以下查询应该可以正常工作(在MSSQL中正常工作):
select a.userID,a.username,b.age,b.sal from <table1> a
inner join
(select userID,MAX(age) age,MAX(sal) sal from <table2> group by userID) b
on a.userID=b.userID