Mysql实战详解3：Mysql查看是否使用到索引

mysql数据库创建索引优化之后，在查询时想看下是否使用到索引，

使用执行计划查看：

mysql> explain  SELECT * FROM tb_user
 WHERE STATUS=1 limit 0,20;
+----+-------------+----------------+------------+------+----------------------+----------------------+---------+-------+-------+----------+-------+
| id | select_type | table          | partitions | type | possible_keys        | key                  | key_len | ref   | rows  | filtered | Extra |
+----+-------------+----------------+------------+------+----------------------+----------------------+---------+-------+-------+----------+-------+
|  1 | SIMPLE      | tb_news_online | NULL       | ref  | idx_tb_news_online_9 | idx_tb_news_online_9 | 5       | const | 99494 |      100 | NULL  |
+----+-------------+----------------+------------+------+----------------------+----------------------+-