[Solved] Why does the LEAD function return NULL for the last row in a partition? — Ans: Because there is no next row after the last row | SQL

SQL - Advanced Window Functions

Why does the LEAD function return NULL for the last row in a partition?

ABecause NULL is the default value for all rows

BBecause there is no next row after the last row

CBecause the last row is excluded by default

DBecause LEAD only works on even-numbered rows

Step-by-Step Solution

Solution:

Step 1: Understand LEAD behavior at partition end
The LEAD function looks forward to the next row; if none exists, it returns NULL.
Step 2: Eliminate incorrect options
LEAD works on all rows, does not exclude last row, and NULL is not default for all rows.
Final Answer:
Because there is no next row after the last row -> Option B
Quick Check:
LEAD returns NULL when no next row exists [OK]

Quick Trick: Last row LEAD returns NULL, no next row exists [OK]

Common Mistakes:

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Why does the LEAD function return NULL for the last row in a partition?