1
你好,我有這個疑問指數
SELECT * FROM customers WHERE height > 180 AND height < 200
,這裏是適用於它的explain
結果:
mysql> explain SELECT * FROM customers WHERE height > 180 AND height < 200;
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
| 1 | SIMPLE | customers | ALL | height | NULL | NULL | NULL | 10423 | Using where |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
注意這裏是字段height
一個指數,沒有被拿起,不知何故...
該height
字段是一個整數。我不知道。我期待它被使用,並且type
成爲range
任何人?
您能否包含高度指數的定義? –
向我們展示了實際的客戶結構表。 –
桌子上有多少記錄落在該高度範圍內? – Kickstart