Mysql: 21 best practices for performance optimization 5 [using equivalent types of _ MySQL during Join tables

Mysql: 21 best practices for performance optimization 5 [use and index equivalent columns when joining a table] bitsCN.com

When you Join a table, use a column of equivalent type and index it.

If your application has many JOIN queries, you should confirm that the Join fields in the two tables are indexed. In this way, MySQL will launch a mechanism to optimize the Join SQL statement for you.
In addition, these fields used for Join should be of the same type. For example, if you want to Join a DECIMAL field with an INT field, MySQL cannot use their indexes. For those STRING types, the same character set is required. (The character sets of the two tables may be different ).

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