[Solved] Consider this SQL query:SELECT * FROM A CROSS JOIN B WHERE A.id = B.id;What is the main issue with this query? | SQL

SQL - Advanced Joins

Consider this SQL query:
SELECT * FROM A CROSS JOIN B WHERE A.id = B.id;
What is the main issue with this query?

AIt will cause a syntax error because CROSS JOIN cannot have WHERE clause.

BIt updates tables A and B unintentionally.

CIt returns no rows because CROSS JOIN filters all rows.

DIt produces the same result as INNER JOIN but less efficiently.

Step-by-Step Solution

Solution:

Step 1: Understand CROSS JOIN with WHERE filter
CROSS JOIN creates all pairs, then WHERE filters pairs where A.id = B.id.
Step 2: Compare with INNER JOIN
This is equivalent to INNER JOIN on A.id = B.id but less efficient because CROSS JOIN generates many unnecessary pairs first.
Final Answer:
It produces the same result as INNER JOIN but less efficiently. -> Option D
Quick Check:
CROSS JOIN + WHERE = INNER JOIN behavior [OK]

Quick Trick: CROSS JOIN + WHERE = INNER JOIN but slower [OK]

Common Mistakes:

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