About MySQL Federated index

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CREATE   table   ' Uniontest ' (    ' id '   int (one)   not   NULL   auto_increment,    ' Menuname '   varchar ( ); DEFAULT   NULL ,    ' url '   varchar ( ); DEFAULT   NULL ,    PRIMARY   key   (' id '),    UNIQUE   KEY   ' U_index ' (' menuname ', ' url ') ) Engine=innodb auto_increment=5  DEFAULT   charset=utf8

Set up the database first, setting the Menuname and URL as the federated index

A few things to note:

1. When inserting data, MySQL has checked the uniqueness of menuname and URL two columns at the same time.

Such as:

INSERT into Uniontest (' menuname ', ' url ') VALUES (' Order Management ', ' aaa.php ') success

INSERT into Uniontest (' menuname ', ' url ') VALUES (' Order Management ', ' bbb.php ') success

INSERT into Uniontest (' menuname ', ' url ') VALUES (' Order Management 2 ', ' aaa.php ') success

INSERT into Uniontest (' menuname ', ' url ') VALUES (' Order Management ', ' aaa.php ') failed

2, at the time of inquiry

Explain SELECT * from uniontest where menuname = ' order management ' used to index

Explain SELECT * from uniontest WHERE menuname = ' order management ' and URL = ' aaa.php '; Use to Index

Explain SELECT * from uniontest WHERE url = ' aaa.php '; The index is not used

Followed the principle of the leftmost priority of the Federated index.

About MySQL Federated index