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This article mainly shows you "MySQL 5.5 how to delete the index", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "MySQL 5.5 how to delete the index" this article.

Mysql > show keys from dept2

+ +-+

| | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

+ +-+

| | dept2 | 0 | PRIMARY | 1 | deptno | A | 4 | NULL | NULL | | BTREE |

| | dept2 | 1 | idx_dept2_deptno | 1 | deptno | A | 4 | NULL | NULL | | BTREE |

| | dept2 | 1 | idx_dept2_report_date | 1 | report_date | A | 4 | NULL | NULL | YES | BTREE |

+ +-+

3 rows in set (0.00 sec)

Method ①

Mysql > drop index idx_dept2_deptno on dept2

Query OK, 0 rows affected (0.02 sec)

Records: 0 Duplicates: 0 Warnings: 0

Mysql > show keys from dept2

+ +-+

| | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

+ +-+

| | dept2 | 0 | PRIMARY | 1 | deptno | A | 4 | NULL | NULL | | BTREE |

| | dept2 | 1 | idx_dept2_report_date | 1 | report_date | A | 4 | NULL | NULL | YES | BTREE |

+ +-+

2 rows in set (0.00 sec)

-- method ②

Mysql > alter table dept2 drop index idx_dept2_report_date

Query OK, 0 rows affected (0.05 sec)

Records: 0 Duplicates: 0 Warnings: 0

Mysql > show keys from dept2

+- -+

| | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

+- -+

| | dept2 | 0 | PRIMARY | 1 | deptno | A | 4 | NULL | NULL | | BTREE |

+- -+

1 row in set (0.00 sec)

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