Mysql Index Optimization

Indexes after a single-table range query are invalidated

Double-table left and right connections to make an index use each other

Three tables using small result sets to drive large table results, first optimize the parentheses inside the SQL, to ensure that the join is driven on the table on the field is indexed

Index invalidation (Common Cause)

full-time matching best left  -hand rule if it is a composite index, make sure that the leftmost index column must have  no, full table scan  * in use ! = or <> when the index cannot be used, it causes a full table scan  is NULL  is NOT NULL also cannot use index like percent plus right like to start with wildcards '%SDF ', index invalidation, full table scan string without single quotes, index invalidation less with or, index invalidation when connected with him

　　

　　

　　

　　

　　　　

Mysql Index Optimization