选择语句中的 SQL 条件列数据返回
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SQL Conditional column data return in a select statement
提问by JL.
Here is a simplication of the problem: I have a select that looks like this:
这是问题的简化：我有一个看起来像这样的选择：
Select ID, Assignee, WorkStream from assignees;
And a snap shot of the data returned looked like this
返回的数据快照如下所示
1|Joe Soap|Internal
2|Mrs Balls|External
What I would like to do is have the select not display the Assignee name if the worksteam is internal. Instead to display the Workstream.
如果工作组是内部的，我想做的是选择不显示受让人名称。而是显示工作流。
So for example the outcome I want to achieve would be this:
例如，我想要实现的结果是：
1|Internal|Internal
2|Mrs Balls|External
I hope this makes sense? Basically a conditional select that can detect if a certain column contains a certain value, then replace another columns value with [whatever].
我希望这是有道理的？基本上是一个条件选择，可以检测某个列是否包含某个值，然后用 [whatever] 替换另一个列的值。
Thanks in advance!
提前致谢！
EDIT I want to achieve something like this:
编辑我想实现这样的目标：
Select ID, if (workstream='internal' select Workstream as Assignee - else - select Assignee as Assigneee), WorkStream from assignees;
回答by Lieven Keersmaekers
You didn't mention your DBMS but a searched CASEstatement works in all major DBMS's I know off.
您没有提到您的 DBMS，但搜索CASE语句适用于我所知道的所有主要 DBMS。
SELECT ID
, CASE WHEN WorkStream = 'Internal'
THEN WorkStream
ELSE Assignee
END AS Assignee
, Workstream
FROM assignees
Reference: MSDN
参考：MSDN
CASE
Evaluates a list of conditions and returns one of multiple possible result expressions.
案件
评估条件列表并返回多个可能的结果表达式之一。
回答by Pongsathon.keng
SELECT ID,
CASE WorkStream WHEN 'Internal' THEN 'INTERNAL' ELSE Assignee as Assignee, WorkStream from assignees
I hope this help.
我希望这会有所帮助。
