[Solved] Which SQL statement correctly uses LAG to retrieve the previous score ordered by player_id? — Ans: SELECT player_id, score, LAG(score) OVER (ORDER BY player_id) AS prev_score... | SQL

SQL - Advanced Window Functions

Which SQL statement correctly uses LAG to retrieve the previous score ordered by player_id?

ASELECT player_id, score, LAG(score) OVER (ORDER BY player_id) AS prev_score FROM Players;

BSELECT player_id, score, LAG(score ORDER BY player_id) AS prev_score FROM Players;

CSELECT player_id, score, LAG(score) AS prev_score ORDER BY player_id FROM Players;

DSELECT player_id, score, LAG(score, 1) FROM Players ORDER BY player_id;

Step-by-Step Solution

Solution:

Step 1: Recall LAG syntax
LAG(column) OVER (ORDER BY column) is the correct syntax to get previous row's value ordered properly.
Step 2: Analyze options
SELECT player_id, score, LAG(score) OVER (ORDER BY player_id) AS prev_score FROM Players; correctly uses LAG with OVER and ORDER BY inside parentheses.
SELECT player_id, score, LAG(score ORDER BY player_id) AS prev_score FROM Players; misplaces ORDER BY inside LAG.
SELECT player_id, score, LAG(score) AS prev_score ORDER BY player_id FROM Players; places ORDER BY outside window function.
SELECT player_id, score, LAG(score, 1) FROM Players ORDER BY player_id; orders the entire query but misses OVER clause.
Final Answer:
Option A -> Option A
Quick Check:
LAG requires OVER with ORDER BY inside [OK]

Quick Trick: LAG needs OVER(ORDER BY ...) clause [OK]

Common Mistakes:

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Which SQL statement correctly uses LAG to retrieve the previous score ordered by player_id?