PostgreSQL - Joins in PostgreSQL
Which of the following best describes the number of rows returned by a CROSS JOIN of a table with 3 rows and another with 4 rows?
Which of the following best describes the number of rows returned by a CROSS JOIN of a table with 3 rows and another with 4 rows?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Calculate rows from each table
The first table has 3 rows, and the second has 4 rows.Step 2: Multiply rows for CROSS JOIN
CROSS JOIN returns the Cartesian product, so total rows = 3 * 4 = 12.Final Answer:
12 rows -> Option CQuick Check:
Rows after CROSS JOIN = 3 * 4 = 12 [OK]
Quick Trick: Multiply row counts of both tables for CROSS JOIN result [OK]
Common Mistakes:
- Adding row counts instead of multiplying
- Confusing with INNER JOIN row counts
- Ignoring one table's row count
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