Sql Performance UNION vs OR

sql

performance

best-practices

indexing

byNikita Barsukov·Dec 21, 2024

When the battle is on with UNION vs. OR in SQL, all eyes are on index utilization. UNION provides each query its own battlefield, optimizing index usage:

-- Go TEAM UNION!
SELECT column FROM table WHERE conditionA
UNION ALL
SELECT column FROM table WHERE conditionB;

Where UNION ALL is the Olympian, outperforming UNION by not breaking a sweat eliminating duplicates. Meanwhile, OR sometimes gets tangled in the thick of full table scans, slowing it down. However, the performance of these SQL athletes can *vary based on your stadium (data), so keep in mind to warm up with your actual data.

Replace the 'OR' team with 'IN'

Swap your OR team with IN team when you're juggling many values for the same column to score performance improvement:

-- TEAM IN stepping up the game!
SELECT column FROM table WHERE column IN (value1, value2, ...);

This strategy simplifies the game while enhancing performance. Just remember to coach your innodb table types appropriately - it's all in the indexing!

Evaluating the performance league

It isn't sufficient to pick an SQL favorite from UNION and OR based purely on speed - their performance differs backstage:

Rows in the Spotlight: UNION is efficient in browsing through fewer rows, leveraging indexes.
Clarity of Play: With OR, you get clearer conditions within the same column. But UNION divides different conditions like no team does.
Handling Sub-queries: Grouping OR conditions with complex sub-queries can be more tiring than breaking them into UNION players.
Understand Your Coach: Make sure you profile and test your queries, as SQL coaches (database optimizers) behave differently with different team statistics and data distributions.

Professional player's move - benchmarking

Benchmark is the personal coach to evaluate and pump up your game:

Get your hands on MySQL query profiler to delve into query performance.
Collate execution times for UNION, UNION ALL, and OR.
Keep an eye on the game plan (execution plan) for potential skill improvements.
Scrutinize the players under spotlight (rows examined) to assess query workload.

Updates in the gaming arena

Stay updated in the ever-changing gaming arena (database version updates):

Stay tuned for new coaches (optimizer improvements) who could take OR conditions to grand leagues.
Revisit your benchmarks after upgrading your gaming arena to assure continued performance.