SQL to find the number of distinct values in a column

Question

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

• SELECT DISTINCT column_name FROM table_name;
• SELECT column_

Answer 1

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
/

Answer 2

You can use the DISTINCT keyword within the COUNT aggregate function:

SELECT COUNT(DISTINCT column_name) AS some_alias FROM table_name

This will count only the distinct values for that column.

Answer 3

**

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

**

Select count(distinct(Column_Name)) from TableName

Answer 4

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]

Answer 5

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

This will give count of distinct group of columns.

Answer 6

select Count(distinct columnName) as columnNameCount from tableName