mysql 计算唯一行值
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mysql count unique row values
提问by love
TABLE quotation
TABLE quotation
id clientid
1 25
2 25
3 25
4 25
5 26
How can I query how many different clients exist in TABLE quotation? I don't want duplicate entries to be counted more than once.
如何查询中存在多少个不同的客户端TABLE quotation？我不希望重复的条目被计算不止一次。
I need the answer to be 2, in 1 row, because the only non-duplicated entries are (25, 26).
我需要的答案是2，在 1 行中，因为唯一的非重复条目是 ( 25, 26)。
回答by octopusgrabbus
I tried the following on a MySQL 5.x database.
我在 MySQL 5.x 数据库上尝试了以下操作。
id is an integer and clientid is an integer. I populated with two rows:
id 是一个整数，clientid 是一个整数。我填充了两行：
id clientid
1 25
2 25
This SQL query will print the rows that have exactly 2 elements:
此 SQL 查询将打印恰好具有 2 个元素的行：
select * from test1 group by clientid having count(*) = 2;
If you want 2 or more elements, replace = 2in the example above with >= 2.
如果您需要 2 个或更多元素，请= 2在上面的示例中替换为>= 2.
select * from test1 group by clientid having count(*) >= 2;
回答by Carl Schulz
If you want to count the total number of unique entries this will return a number in column count.
如果您想计算唯一条目的总数，这将返回列数中的一个数字。
SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY clientid having count(*) > 1) t1
If you want to count the total number of entries with duplicate rows then use the following mysql.
如果要计算具有重复行的条目总数，请使用以下 mysql.
SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY clientid having count(*) >= 2) t1
回答by love
I find a way out
我找到出路
SELECT COUNT(*) as total FROM (SELECT COUNT(*) FROM quotation GROUP BY
clientid) t1
回答by Gajendra Bang
SELECT clientid, COUNT(clientid) FROM quotation
GROUP BY clientid
