Join Cardinality Across Joins

A Virtusa data integration pipeline receives two staging tables containing repeated business keys and missing values. Write a PostgreSQL query that compares how different join types affect the number of returned records.

The tables contain the following values:

Requirements

1. Calculate the number of records returned by an INNER JOIN on t1.value = t2.value.
2. Calculate the number of records returned by LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN using the same condition.
3. Calculate the number of records returned by a CROSS JOIN.
4. Return one row per join type with columns join_type and record_count, in the order listed above.
5. Account for duplicate values and explain why NULL values do not match using the equality condition.