Is it necessary to have a PRIMARY index AND colname index on the primary key column?
質問
Imagine the following table:
Simple single row table.
Colname = id int(11)
+---------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| tablename | 0 | PRIMARY | 1 | id | A | 1719077 | NULL | NULL | | BTREE | | |
| tablename | 0 | id | 1 | id | A | 1719077 | NULL | NULL | | BTREE | | |
+---------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
That is the dump of show indexes in tablename.
I think this is a 'bug' in the mysql manager I use (ems mysql manager) where when you create a table with a primary key, it will create both a PRIMARY index (the name of the actual index is PRIMARY) and also a primary-key-colname index automatically on table creation.
Is it ok to remove one of these?
Thanks!
解決
Absolutely. The primary key will function just fine as an index.
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