I’m trying to understand database optimization better and keep hearing about indexes in SQL.
I’ve been working with databases for a while now but I’m still confused about what exactly an index does. I know they’re supposed to make queries faster somehow, but I don’t really get the concept.
Can someone break down what an index actually is in simple terms? Like, what happens behind the scenes when you create one?
Also, I’m curious about the practical side - when should I actually use indexes? Are there situations where they might hurt performance instead of helping? I want to make sure I’m not just adding them randomly without understanding the impact.
Any examples or explanations would be really helpful. Thanks!
that’s a great question! ya, looking at your most common queries is a good start, especially what’s in the WHERE clause. composite indexes can be super useful if you often filter by multiple columns, just keep an eye on their impact on performance!
indexes r like shortcuts, man. they help the db find stuff fast instead of scans every row, which is sluggish on big tables. focus on columns in WHERE clauses, but be careful - too many indexes can slow down writes since they gotta b updated when data chngs.
An index acts like a book’s index, allowing the database to locate data quickly without scanning every row. When you create an index on a column, it builds a separate data structure map that correlates values to their storage locations. For instance, I implemented an index on a project where query times dropped from over 30 seconds to under 200 milliseconds simply by indexing the email column. However, be aware that indexes require additional storage and can hinder performance during INSERT, UPDATE, and DELETE operations as they must be maintained. It’s advisable to index columns frequently used in WHERE clauses or JOINs, but avoid those that change often or have low selectivity.