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What Is an Index?
A structure that speeds up finding rows.
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AiTechWorlds
AiTechWorlds
Database indexing speeds up data retrieval by letting the database find rows without scanning everything. This visual guide explains how indexes work, B-trees, composite and covering indexes, tradeoffs, and when not to index.
A structure that speeds up finding rows.
Like an index in a book — jump straight to it.
The database scans every row (slow).
It jumps directly to matching rows.
Balanced trees enable fast lookups.
Automatically indexes the primary key.
Index other frequently queried columns.
Index multiple columns together.
Column order affects which queries benefit.
Index includes all needed columns.
Enforce uniqueness and speed lookups.
Filtering, sorting, and joining.
Indexes slow down inserts and updates.
Indexes take extra disk space.
Hurt write performance and waste space.
EXPLAIN shows if an index is used.
High-variety columns index best.
Tiny tables or rarely queried columns.
Rebuild and monitor over time.
Find slow queries and add targeted indexes.
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