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Trick questions asked by Interviewers.. here is the explaination
1️⃣Both count rows, not values

COUNT(*) counts every row.

COUNT(1) evaluates the constant 1 for every row.

In both cases, the database still counts rows.

2️⃣The optimizer treats them identically

Query optimizers rewrite COUNT(1) into COUNT(*).

Execution plans are the same.

Reality: No performance difference.

3️⃣No NULL checks in either case

1 is never NULL, so COUNT(1) does not filter anything. Same behavior as COUNT(*).

4️⃣Index and storage access are identical

Both queries scan the same data or index pages. No extra I/O, no extra CPU.

Applies to: MySQL, PostgreSQL, Oracle, SQL Server

5️⃣ The "COUNT(1) is faster" myth is outdated This came from very old database engines.

Modern engines fully optimize both.

👉Final Verdict (INTERVIEW SAFE ANSWER)

Neither is faster

Both compile to the same execution plan
Use COUNT(*) for clarity and intent.

[COUNT star vs COUNT 1, SQL interview questions, database performance myths, SQL optimization explained, backend engineering concepts, MySQL Postgres internal]
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