[sql] SQL to find the number of distinct values in a column

I can select all the distinct values in a column in the following ways:

• 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?

select count(*) from 
(
SELECT distinct column1,column2,column3,column4 FROM abcd
) T

This will give count of distinct group of columns.

select count(*) from 
(
SELECT distinct column1,column2,column3,column4 FROM abcd
) T

This will give count of distinct group of columns.

SELECT COUNT(DISTINCT column_name) FROM table as column_name_count;

you've got to count that distinct col, then give it an alias.

An sql sum of column_name's unique values and sorted by the frequency:

SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name ORDER BY 2 DESC;

After MS SQL Server 2012, you can use window function too.

   SELECT column_name, 
   COUNT(column_name) OVER (Partition by column_name) 
   FROM table_name group by column_name ; 

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.

SELECT [columnName], count([columnName]) AS CountOf
FROM [tableName]
GROUP BY [columnName]

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:

select count(distinct my_col)
       + count(distinct Case when my_col is null then 1 else null end)
from my_table
/

**

Using following SQL we can get the distinct column value count in Oracle 11g.

**

Select count(distinct(Column_Name)) from TableName

select Count(distinct columnName) as columnNameCount from tableName 

select count(distinct(column_name)) AS columndatacount from table_name where somecondition=true

You can use this query, to count different/distinct data. Thanks

Count(distinct({fieldname})) is redundant

Simply Count({fieldname}) gives you all the distinct values in that table. It will not (as many presume) just give you the Count of the table [i.e. NOT the same as Count(*) from table]