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When using subqueries, we can use composite indexes. The advantages of using composite indexes are that they can be.
Join
Filtering
Selecting in
The syntax of index is as follows.
index(column_name1column_name2column_name3column_name4............................N)
Let's first create a table and set an index in it.
mysql> create table MultipleIndexDemo - > ( - > id int, - > FirstName varchar(100), - > LastName varchar(100), - > Address varchar(200), - > index(id,LastName,Address) - > ;
Check if the index is successfully created.
mysql> show index from MultipleIndexDemo;
The following is the output.
+-------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | +-------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+ | multipleindexdemo | 1 | id | 1 | id | A | AAAAAAAA | 0 | NULL | NULL | YES | BTREE | AAAAAAAA | AAAAAAAA | AAAAAAAA | YES | | multipleindexdemo | 1 | id | 2 | LastName | A | AAAAAAAA | 0 | NULL | NULL | YES | BTREE | AAAAAAAA | AAAAAAAA | AAAAAAAA | YES | | multipleindexdemo | 1 | id | 3 | Address | A | AAAAAAAA | 0 | NULL | NULL | YES | BTREE | AAAAAAAA | AAAAAAAA | AAAAAAAA | YES | +-------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+ 3 rows in set (0.18 sec)