SQL 查找列中不同值的数量
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SQL to find the number of distinct values in a column
提问by Christian Oudard
I can select all the distinct values in a column in the following ways:
我可以通过以下方式选择列中的所有不同值：
SELECT DISTINCT column_name FROM table_name;SELECT column_name FROM table_name GROUP BY column_name;
SELECT DISTINCT column_name FROM table_name;SELECT column_name FROM table_name GROUP BY column_name;
But how do I get the row count from that query? Is a subquery required?
但是如何从该查询中获取行数？是否需要子查询？
回答by Noah Goodrich
回答by Paul James
This will give you BOTH the distinct column values and the count of each value. I usually find that I want to know both pieces of information.
这将为您提供不同的列值和每个值的计数。我通常发现我想知道这两条信息。
SELECT [columnName], count([columnName]) AS CountOf
FROM [tableName]
GROUP BY [columnName]
回答by David Aldridge
Be aware that Count() ignores null values, so if you need to allow for null as its own distinct value you can do something tricky like:
请注意 Count() 会忽略 null 值，因此如果您需要允许 null 作为其自己的独特值，您可以做一些棘手的事情，例如：
select count(distinct my_col)
+ count(distinct Case when my_col is null then 1 else null end)
from my_table
/
回答by xchiltonx
An sql sum of column_name's unique values and sorted by the frequency:
column_name 的唯一值的 sql 总和并按频率排序：
SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name ORDER BY 2 DESC;
回答by xchiltonx
select count(*) from
(
SELECT distinct column1,column2,column3,column4 FROM abcd
) T
This will give count of distinct group of columns.
这将给出不同列组的计数。
回答by Pete Karl II
SELECT COUNT(DISTINCT column_name) FROM table as column_name_count;
you've got to count that distinct col, then give it an alias.
你必须计算那个不同的 col，然后给它一个别名。
回答by Wayne
select Count(distinct columnName) as columnNameCount from tableName
回答by Nilesh Shinde
**
**
Using following SQL we can get the distinct column value countin Oracle 11g.
使用以下 SQL，我们可以获得Oracle 11g 中的不同列值计数。
**
**
Select count(distinct(Column_Name)) from TableName
回答by Nitika Chopra
select count(distinct(column_name)) AS columndatacount from table_name where somecondition=true
You can use this query, to count different/distinct data. Thanks
您可以使用此查询来计算不同/不同的数据。谢谢
回答by Alper
After MS SQL Server 2012, you can use window function too.
在 MS SQL Server 2012 之后，您也可以使用窗口函数。
SELECT column_name,
COUNT(column_name) OVER (Partition by column_name)
FROM table_name group by column_name ;
