Question

I have only 1 column. I need statistics about it’s values and their usage:

Value | Count
-----------------
NULL  |   41 (91%)
''    |   3  (3%)
'FOO' |   2  (2%)
'BAR' |   1  (1%)

Also I need to perform such query for every column in database. Is there utility to help me with such reports? I asking about Postgresql/Mysql.

Answer 1

select value , count(*) from table 
group by value 

Replace table for your table name and value for your column name

With Percentages:

select value 
 ,count(*)
 ,COUNT(*)/(select cast(COUNT(*) as decimal) as Total from table) as Usage 
 from table 
group by value