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This article is to share with you about the index merge merge index, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Mysql > create index ind_t2_name on T2 (name)

Query OK, 0 rows affected (0.18 sec)

Records: 0 Duplicates: 0 Warnings: 0

Mysql > create index ind_t2_addr on T2 (address)

Query OK, 0 rows affected (0.11 sec)

Records: 0 Duplicates: 0 Warnings: 0

Mysql > explain select * from T2 where name='name44' or address='address888'

| | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |

| | 1 | SIMPLE | T2 | NULL | index_merge | ind_t2_name,ind_t2_addr | ind_t2_name,ind_t2_addr | 63153 | NULL | 2 | 100.00 | Using union (ind_t2_name,ind_t2_addr); Using where |

1 row in set, 1 warning (.53 sec)

In mysql5.5 or previous versions of single tables, only one index can be used, and two indexes cannot be merged. It is best to change or to union all.

Select * from T2 where name='name44' union all select * from T2 where address='address888'

The above is the index merge merge index, the editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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