[Solved] Why does this query fail to find gaps correctly?SELECT num + 1 AS missing FROM seq WHERE num + 1 LEAD(num); | SQL

SQL - Advanced Query Patterns

Why does this query fail to find gaps correctly?

SELECT num + 1 AS missing FROM seq WHERE num + 1 <> LEAD(num);

ALEAD() cannot be used in SELECT clause

Bnum + 1 cannot be used in WHERE clause

CMissing GROUP BY causes error

DLEAD() requires an OVER() clause with ORDER BY

Step-by-Step Solution

Solution:

Step 1: Check LEAD() usage
LEAD() is a window function and must have an OVER() clause specifying order.
Step 2: Identify missing OVER() clause
Without OVER(ORDER BY ...), LEAD() causes syntax error or wrong results.
Final Answer:
LEAD() requires an OVER() clause with ORDER BY -> Option D
Quick Check:
Window functions need OVER() [OK]

Quick Trick: Always use OVER() with LEAD() [OK]

Common Mistakes:

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Why does this query fail to find gaps correctly?