023 MySQL index optimization tips - common cases of index failure

Index optimization summary formula ：
Full value matching my favorite , The leftmost prefix should follow ;
Leading brother can't die , The middle brother can't break ;
Less computation on index columns , After the range, it all fails ;
like 100% right , Overlay index without writing * ;
Unequal control and or, Index failure should be used less ;
var Quotation marks cannot be lost ,  sql It's not hard to be advanced ;

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1、 Full match ： Specify specific values for all columns in the index . In this case , The index works , High execution efficiency

2、 Left most prefix ： Also called the leftmost matching principle , The leftmost matching principle is and MySQL Of InnoDB Storage engine B+Tree The data structures of are closely related , You can read these blogs ：

The first 1 piece ：MySQL Of InnoDB Index references in the storage engine B+Tree

The first 2 piece ：MySQL Official website nomenclature / A collection of difficult words （glossary） Medium B+Tree explain

The first 3 piece ：MySQL in B+Tree, From the binary tree 、 Balanced binary trees 、B-Tree Speak up

3、 Overlay index ： An index contains all the field values to be queried