Finding columns that are NOT NULL in PostgreSQL

No.

This query

SELECT DISTINCT column_name, table_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE column_name IS NOT NULL

will return all the rows that have a value in the column “column_name”.

All rows in that table will always have a value in the column “column_name”.

Do you just need to know how many columns are nullable and how many are non-nullable?

SELECT is_nullable, COUNT(*)
FROM INFORMATION_SCHEMA.COLUMNS
GROUP BY is_nullable;

Count by table name? I think you can use this.

SELECT table_name, is_nullable, count(*)
FROM INFORMATION_SCHEMA.COLUMNS
GROUP BY table_name, is_nullable
ORDER BY table_name, is_nullable;

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