Select tables optimized away
在MySQL Explain plan中的含義是什麼?MySQL中的「Select tables optimized away」的含義Explain plan
explain select count(comment_count) from wp_posts;
+----+-------------+---------------------------+-----------------------------+
| id | select_type | table,type,possible_keys, | Extra |
| | | key,key_len,ref,rows | |
+----+-------------+---------------------------+-----------------------------+
| 1 | SIMPLE | all NULLs | Select tables optimized away|
+----+-------------+---------------------------+-----------------------------+
1 row in set (0.00 sec)
注意:explain plan
輸出編輯爲易讀性。
查詢結果與InnoDB表類似:SELECT MAX(k3)FROM t1 WHERE k1 ='1'AND k2 ='2',其中k1,k2和k3都是鍵的所有部分。 – Ghostrider 2010-07-23 23:05:39