[Solved] What is wrong with this query?SELECT id, name FROM table1 EXCEPT SELECT id FROM table2; — Ans: The number of columns in both SELECTs differ | PostgreSQL

PostgreSQL - Set Operations and Advanced Queries

What is wrong with this query?

SELECT id, name FROM table1 EXCEPT SELECT id FROM table2;

AThe number of columns in both SELECTs differ

BEXCEPT cannot be used with SELECT statements

CThe query is missing a WHERE clause

DThe table names are invalid

Step-by-Step Solution

Solution:

Step 1: Check column counts in both SELECTs
First SELECT returns two columns (id, name), second returns one column (id).
Step 2: Understand EXCEPT requirements
EXCEPT requires both SELECTs to have the same number and compatible types of columns.
Final Answer:
The number of columns in both SELECTs differ -> Option A
Quick Check:
EXCEPT needs equal columns [OK]

Quick Trick: EXCEPT requires same number of columns in both SELECTs [OK]

Common Mistakes:

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What is wrong with this query?