Find the non null columns in SQL Server in a table

Question

I have read many answers but they are all for PL/SQL or Oracle, I could not find anything for Microsoft SQL-Server.

My table :

CREATE TABLE StudentSc         


        

Answer 1

You could achieve it by issuing:

SELECT 
  FORMATMESSAGE('SELECT col = ''%s.%s.%s'' FROM %s.%s HAVING COUNT(*) != COUNT(%s)', 
     QUOTENAME(TABLE_SCHEMA),
     QUOTENAME(TABLE_NAME),
     QUOTENAME(COLUMN_NAME),
     QUOTENAME(TABLE_SCHEMA),
     QUOTENAME(TABLE_NAME),
     QUOTENAME(COLUMN_NAME)
  )
FROM INFORMATION_SCHEMA.COLUMNS
WHERE IS_NULLABLE = 'YES';

db<>fiddle demo

It will generate script for checking individual column.

HAVING COUNT(*) != COUNT(col_name) -- it means that column contains at least single NULL

HAVING COUNT(col_name) = 0 AND COUNT(*) != 0 -- it means all values in columns are NULL

This approach could be polished with using STRING_AGG to get single query per table and with dynamic SQL you could avoid the need of copying the query.

EDIT:

Fully baked-solution:

DECLARE @sql NVARCHAR(MAX);

SELECT @sql = STRING_AGG(
  FORMATMESSAGE('SELECT table_schema = ''%s''
                        ,table_name = ''%s''
                        ,table_col_name = ''%s'' 
                        ,row_num = COUNT(*)
                        ,row_num_non_nulls = COUNT(%s)
                        ,row_num_nulls = COUNT(*) - COUNT(%s)
                 FROM %s.%s', 
     QUOTENAME(TABLE_SCHEMA),
     QUOTENAME(TABLE_NAME),
     QUOTENAME(COLUMN_NAME),
     QUOTENAME(COLUMN_NAME),
     QUOTENAME(COLUMN_NAME),
     QUOTENAME(TABLE_SCHEMA),
     QUOTENAME(TABLE_NAME),
     QUOTENAME(COLUMN_NAME)), ' UNION ALL' + CHAR(13)
               ) WITHIN GROUP(ORDER BY TABLE_SCHEMA, TABLE_NAME)

FROM INFORMATION_SCHEMA.COLUMNS
WHERE IS_NULLABLE = 'YES'
  AND TABLE_NAME = ?        -- filter by table name
  AND TABLE_SCHEMA = ?;     -- filter by schema name

SELECT @sql;
EXEC(@sql);

db<>fiddle demo

Output:

+---------------+-----------------+------------------+----------+--------------------+---------------+
| table_schema  |   table_name    | table_col_name   | row_num  | row_num_non_nulls  | row_num_nulls |
+---------------+-----------------+------------------+----------+--------------------+---------------+
| [dbo]         | [StudentScore]  | [Student_Name]   |       7  |                 6  |             1 |
| [dbo]         | [StudentScore]  | [Student_Score]  |       7  |                 5  |             2 |
+---------------+-----------------+------------------+----------+--------------------+---------------+    

Answer 2

Perhaps you want to look at INFORMATION_SCHEMA.COLUMNS. The column IS_NULLABLE provides this information.

Note that the INFORMATION_SCHEMA tables (well, they are really views) are Standard SQL, so this information is available in most database. Oracle has not (yet?) adopted them.