如何向MySQL表添加索引？ [英] How do I add indices to MySQL tables?

问题描述

我有一个非常大的MySQL表，大约有150,000行数据。目前，当我尝试并运行时

I've got a very large MySQL table with about 150,000 rows of data. Currently, when I try and run

SELECT * FROM table WHERE id = '1';

代码运行正常，因为ID字段是主索引。
但是，最近对于项目中的开发，我必须通过另一个字段搜索数据库。例如

the code runs fine as the ID field is the primary index. However, recently for a development in the project, I have to search the database by another field. For example

SELECT * FROM table WHERE product_id = '1';

此字段之前未编入索引，但是，我已将其添加为索引，但是当我试着运行上面的查询，结果很慢。 EXPLAIN查询显示，当我已经添加了一个索引时，product_id字段没有索引，因此查询从20分钟到30分钟的任何位置返回单行。

This field was not previously indexed, however, I've added it as an index, but when I try to run the above query, the results is very slow. An EXPLAIN query reveals that there is no index for the product_id field when I've already added one and as a result the query takes any where from 20 minutes to 30 minutes to return a single row.

我的完整EXPLAIN结果是：

My full EXPLAIN results are:

| id | select_type | table | type | possible_keys        | key  | key_len | ref  | rows      | Extra       |
+----+-------------+-------+------+----------------------+------+---------+------+------+------------------+
|  1 | SIMPLE      | table | ALL  | NULL                 | NULL | NULL    | NULL |    157211 | Using where |
+----+-------------+-------+------+----------------------+------+---------+------+------+------------------+

注意我可能会有所帮助我们只看了一眼，ID字段存储为INT，而PRODUCT_ID字段存储为VARCHAR。这可能是问题的根源吗？

It might be helpful to note that I've just taken a look and ID field is stored as INT whereas the PRODUCT_ID field is stored as VARCHAR. Could this be the source of the problem?

推荐答案

ALTER TABLE `table` ADD INDEX `product_id` (`product_id`)

绝不比较整数到字符串。如果 id 是 int ，请删除引号。

Never compare integer to strings in MySQL. If id is int, remove the quotes.

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