Shulou(Shulou.com)06/01 Report--

Compound index principle: high-speed racing source code construction

Leftmost prefix principle: enterprise E: 217 1793

Index (a _

1. Each query must have a, such as ab,ac,abc. If there is no a, only bc query will be invalid.

2. With or in the query, the query fails

3. The query is invalid with% * in the query.

4. Where asides * and b > and caches *, c will not move the index

Whether the index is valid or not can be analyzed using explain select * in mysql.

Mainly check type, possiable_key to see performance optimization, execution time is not the main implementation reference standard.

If you don't walk the index, you can force it through: force index ().

Therefore, we should carefully consider the scene selection of compound index and single index!

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