MySQL 分组时如何从表格中选择最长的“字符串”
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How do I select the longest 'string' from a table when grouping
提问by user1336827
Example:
例子：
SELECT partnumber, manufacturer, condition, SUM(qty), AVG(price), description FROM parts
WHERE [something]
GROUP BY partnumber, manufacturer, condition
I have some descriptions that are blank, and there can be many partnumber, manufacturer, condition values, and on the group it seems to take the first description available, which can be blank. Id like to get the longest description available.
我有一些描述是空白的，可能有很多零件号、制造商、条件值，并且在组中似乎采用第一个可用的描述，它可以是空白的。我想获得最长的可用描述。
i tried this:
我试过这个：
MAX(LENGTH(description))
however that returns the number of characters in the string. Is it possible to do what im trying to do in MySQL?
但是，它返回字符串中的字符数。是否可以做我在 MySQL 中尝试做的事情？
回答by StilesCrisis
Try ORDER BY LENGTH(description) DESCand use LIMIT 1to only get the largest.
尝试ORDER BY LENGTH(description) DESC并使用LIMIT 1只获得最大的。
回答by Scott Nelson
ORDER BY LENGTH(description) DESC LIMIT 1
This will sort the results from longest to shortest and give the first result (longest.)
这会将结果从最长到最短排序，并给出第一个结果（最长）。
回答by eggyal
SELECT partnumber, manufacturer, `condition`, SUM(qty), AVG(price), description
FROM parts
WHERE [something] AND LENGTH(description) = (
SELECT MAX(LENGTH(description))
FROM parts AS p
WHERE p.partnumber = parts.partnumber
AND p.manufacturer = parts.manufacturer
AND p.condition = parts.condition
)
GROUP BY partnumber, manufacturer, `condition`
回答by user1336827
It seems i answered my own question, MAX(description) seems to work just fine.
看来我回答了我自己的问题，MAX(description) 似乎工作得很好。
回答by Tushar Kesare
MAX(LENGTH(description)) returns length of longest value in Description column.
MAX(LENGTH(description)) 返回描述列中最长值的长度。
