SQL Indexes: Boost Your Query Performance

Database indexes are data structures that improve the speed of data retrieval operations. Think of them like a book's index — instead of reading every page to find information, you look it up in the index first.

Without an index, the database must scan every row (full table scan) to find matching records. With an index on the searched column, it can jump directly to the relevant rows using a B-tree or hash structure.

CREATE INDEX index_name ON table_name(column_name) adds an index. Composite indexes on multiple columns help queries that filter on those columns together. But indexes aren't free — they slow down INSERT/UPDATE operations and use disk space.

Best practices: index columns used in WHERE, JOIN, and ORDER BY clauses. Don't over-index — each index adds overhead. Use EXPLAIN or EXPLAIN QUERY PLAN to see if your queries are using indexes effectively.

Experiment with indexes in CompileZ's SQL editor. Create tables with and without indexes and compare query plans.