SQL 如何在 db2 列选择查询中使用案例
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How to use case in db2 column select query
提问by JulioBordeaux
I have a table in which there is a varchar column 'someid'and some timestamp columns:
'date_1', ... , date_4and 'xdate_1', ... , xdate_4I am trying to select two of them depending on 'someid' value, but had no luck until now. I am sure that this is syntax, googling also didn't help as all the examples were similar to my query.
我有一个表，其中有一个VARCHAR列'someid'和一些时间戳列：
'date_1', ... , date_4和'xdate_1', ... , xdate_4我想选择其中两个依赖于“someid的价值，但没有运气，直到如今。我确信这是语法，谷歌搜索也没有帮助，因为所有示例都与我的查询相似。
Heres what I'm trying to do:
这是我想要做的：
select
case
when someid = 1 then date_1
when someid = 2 then date_2
when someid = 3 then date_3
when someid = 4 then date_4
,case
when someid = 1 then xdate_1
when someid = 2 then xdate_2
when someid = 3 then xdate_3
when someid = 4 then xdate_4
from mytable;
回答by juergen d
You forgot the end
你忘记了 end
select
case
when someid = 1 then date_1
when someid = 2 then date_2
when someid = 3 then date_3
when someid = 4 then date_4
end as col1
,case
when someid = 1 then xdate_1
when someid = 2 then xdate_2
when someid = 3 then xdate_3
when someid = 4 then xdate_4
end as col2
from mytable;
回答by Gordon Linoff
As a note, if someidis a character column, then you should use character comparisons:
请注意，如果someid是字符列，则应使用字符比较：
select (case when someid = '1' then date_1
when someid = '2' then date_2
when someid = '3' then date_3
when someid = '4' then date_4
end),
. . .
from mytable;
