Counting null and non-null values in a single query

Question

I have a table

create table us
(
 a number
);

Now I have data like:

a
1
2
3
4
null
null
null
8
9

Now I need

Answer 1

Try this..

SELECT CASE 
         WHEN a IS NULL THEN 'Null' 
         ELSE 'Not Null' 
       END a, 
       Count(1) 
FROM   us 
GROUP  BY CASE 
            WHEN a IS NULL THEN 'Null' 
            ELSE 'Not Null' 
          END 

Answer 2

This works for Oracle and SQL Server (you might be able to get it to work on another RDBMS):

select sum(case when a is null then 1 else 0 end) count_nulls
     , count(a) count_not_nulls 
  from us;

Or:

select count(*) - count(a), count(a) from us;

Answer 3

If you're using MS Sql Server...

SELECT COUNT(0) AS 'Null_ColumnA_Records',
(
    SELECT COUNT(0)
    FROM your_table
    WHERE ColumnA IS NOT NULL
) AS 'NOT_Null_ColumnA_Records'
FROM your_table
WHERE ColumnA IS NULL;

I don't recomend you doing this... but here you have it (in the same table as result)

Answer 4

Here are two solutions:

Select count(columnname) as countofNotNulls, count(isnull(columnname,1))-count(columnname) AS Countofnulls from table name

OR

Select count(columnname) as countofNotNulls, count(*)-count(columnname) AS Countofnulls from table name

Answer 5

I had a similar issue: to count all distinct values, counting null values as 1, too. A simple count doesn't work in this case, as it does not take null values into account.

Here's a snippet that works on SQL and does not involve selection of new values. Basically, once performed the distinct, also return the row number in a new column (n) using the row_number() function, then perform a count on that column:

SELECT COUNT(n)
FROM (
    SELECT *, row_number() OVER (ORDER BY [MyColumn] ASC) n
    FROM (
        SELECT DISTINCT [MyColumn]
                    FROM [MyTable]
        ) items  
) distinctItems

Answer 6

for non nulls

select count(a)
from us

for nulls

select count(*)
from us

minus 

select count(a)
from us

Hence

SELECT COUNT(A) NOT_NULLS
FROM US

UNION

SELECT COUNT(*) - COUNT(A) NULLS
FROM US

ought to do the job

Better in that the column titles come out correct.

SELECT COUNT(A) NOT_NULL, COUNT(*) - COUNT(A) NULLS
FROM US

In some testing on my system, it costs a full table scan.