Some optimization recommendations for MySQL database indexing

1, independent index column. An index cannot be part of an expression, which means that the index column cannot participate in any calculation and function methods (punch parameters), and so on.

2, do not use the index arbitrarily. It is not said that adding an index to all query columns after the WHERE condition will definitely improve query performance.

3. When there are more than two indexed columns in the where, you should consider using a multi-column index.

4. Note The order of index columns (for multi-column indexes). Put the highest selectivity in front, such as two indexes, one is a professional class, it is obvious that the screening profession is faster than the screening class, because the professional data is much less than the class.

To be Continued ...

Some optimization recommendations for MySQL database indexing