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?
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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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