如何计算数据库列中所有不同值的发生次数？ [英] How to count number of occurences for all different values in database column?

问题描述

我有一个Postgre数据库，说10列。第五列称为 column5 。数据库中有100行， column5 的可能值为 c5value1，c5value2，c5value3 ... c5value29，c5value30 。我想打印一个表，显示每个值发生多少次。

I have a Postgre database that has say 10 columns. The fifth column is called column5. There are 100 rows in the database and possible values of column5 are c5value1, c5value2, c5value3...c5value29, c5value30. I would like to print out a table that shows how many times each value occurs.

所以表格如下所示：

Value(of column5)          number of occurrences of the value
     c5value1                              1
     c5value2                              5
     c5value3                              3
     c5value4                              9
     c5value5                              1
     c5value6                              1
        .                                  .
        .                                  .
        .                                  .

这是什么命令？
感谢您的帮助

What is the command that does that? Thanks for help

推荐答案

按照您感兴趣的列分组，然后使用count获取行数在每个组中：

Group by the column you are interested in and then use count to get the number of rows in each group:

SELECT column5, COUNT(*)
FROM table1
GROUP BY column5

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