Taken from Kai Sassnowskis' talk at LARACON EU from 2018 source:
- Indeces aren't used when using functions (like e.G. YEAR() or MONTH()), use e.G. BETWEEN instead.
- If not sure what is happening, use an EXPLAIN before your statement.
- Multi column indeces go from left to right and you can not skip columns, so the defined order in the index matters.
- An index and a query always have to go together.
- Inequality Operators: Which query is more important? Is the introduction of another index the right approach?
- "Indexing is my concern", not of others