MySQL GROUP_CONCAT() 和 CONCAT_WS() 的区别？
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Difference between GROUP_CONCAT() and CONCAT_WS()?
提问by Matt
I have searched unsuccessfully for a satisfactory explanation on the difference between GROUP_CONCAT()and CONCAT_WS().
我已经搜索不成功上的区别一个满意的解释GROUP_CONCAT()和CONCAT_WS()。
Are they as closely related as I think they are?
它们是否像我认为的那样密切相关？
What are the differences in usage, speed, etc. between these two functions?
这两个功能在用法、速度等方面有什么区别？
回答by Kalpesh
GROUP_CONCATis used when you want to have non-NULL values from different column rows in a single row. For this you need to have GROUP BY to work.
GROUP_CONCAT当您希望在一行中包含来自不同列行的非 NULL 值时使用。为此，您需要让 GROUP BY 工作。
CONCAT_WSis to join two or more strings.
CONCAT_WS是连接两个或多个字符串。
Example,
例子，
GROUP_CONCAT(CONCAT_WS(' ', firstname, lastname) ORDER BY id ASC SEPARATOR ',');
GROUP_CONCAT(CONCAT_WS(' ', firstname, lastname) ORDER BY id ASC SEPARATOR ',');
Outputs something like,
输出类似，
John Doe,Blah Blah,Tom Cruise,Lorem Ipsum
John Doe,Blah Blah,Tom Cruise,Lorem Ipsum
here space between the name is because of CONCAT_WS,
while whole result in one row is because of GROUP_CONCAT
这里名称之间的空格是因为CONCAT_WS，而一行中的整个结果是因为GROUP_CONCAT
回答by cellepo
Pictorial difference:
图片差异：
http://www.w3resource.com/mysql/string-functions/mysql-concat_ws-function.php
http://www.w3resource.com/mysql/string-functions/mysql-concat_ws-function.php
GROUP_CONCATbelow
以下GROUP_CONCAT
