MySQL GROUP BY 返回第一条记录
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GROUP BY return the first record
提问by ntan
As far as I know mysql GROUP BY groups to the last record found.
据我所知 mysql GROUP BY 组找到的最后一条记录。
Is there any solution to GROUP BY the first record?
GROUP BY第一条记录有什么解决办法吗？
I have setup the ORDER in SQL command and I need GROUP BY return the first record and not the last.
我已经在 SQL 命令中设置了 ORDER，我需要 GROUP BY 返回第一条记录而不是最后一条记录。
EDIT
编辑
Here is the Query
这是查询
SELECT
DISTINCT(master.masterID),
langData.*,
master.*
FROM master_table as master
INNER JOIN lang_table as langData ON
langData.masterID=master.masterID
GROUP BY master.masterID
ORDER BY
CASE
WHEN langData.lang='currentLang' THEN 1 ELSE 999 END ,
master.name desc LIMIT 0,10
The query above select the masterIDfor multi language table and suppose to return FIRST the records in currentLangand order them by name AND THEN all other languages.
上面的查询选择了masterID多语言表，并假设首先返回记录currentLang并按名称排序，然后是所有其他语言。
Don't ask me why I don't set the language in JOIN. This is the way to be done.
不要问我为什么不在JOIN里设置语言。这是要完成的方法。
So everything works fine so far expect the scenario that I have a record with languages enand fr. If currentLangis enthen based on
所以到目前为止一切正常，期待我有语言en和fr. 如果currentLang是en再依据
langData.lang='currentLang' THEN 1 ELSE 999 END
the enorder is 1 and frorder is 999 and instead of getting the value of enI get the value of fr.
该en订单是1和fr秩序是和999不是获取价值的en，我得到的价值fr。
That's why I want to group to the first row.
这就是为什么我想分组到第一行。
采纳答案by Quassnoi
I assume you are talking of something like
我假设你在谈论类似的事情
SELECT *
FROM mytable
GROUP BY
column
You shouldn't use unaggregated expressions in GROUP BYunless they are all same within the group.
GROUP BY除非它们在组内都相同，否则不应在其中使用未聚合的表达式。
If you want to return the record holding the least value of an expression within a group, use this:
如果要返回组中包含表达式最小值的记录，请使用以下命令：
SELECT mo.*
FROM (
SELECT DISTINCT column
FROM mytable
) md
JOIN mytable mo
ON mo.id =
(
SELECT id
FROM mytable mi
WHERE mi.column = md.column
ORDER BY
mi.column, mi.someorder
LIMIT 1
)
回答by Daniel A. White
Add LIMIT 1to your query.
添加LIMIT 1到您的查询中。
