MySQL explain:修订间差异

来自WHY42
Riguz留言 | 贡献
Riguz留言 | 贡献
无编辑摘要
第1行: 第1行:
= 例子 =
= Explain =
Explain用来查看执行计划。可用于<span class="article-label">SELECT</span>, <span class="article-label">DELETE</span>, <span class="article-label">INSERT</span>, <span class="article-label">REPLACE</span>, and <span class="article-label">UPDATE</span> statements
 
== 例子 ==
<pre>
<pre>
mysql> explain SELECT COUNT(*) FROM vehicle_prod WHERE fin LIKE '%00000' \G
mysql> explain SELECT COUNT(*) FROM vehicle_prod WHERE fin LIKE '%00000' \G

2021年5月3日 (一) 10:19的版本

Explain

Explain用来查看执行计划。可用于, , , , and statements

例子

mysql> explain SELECT COUNT(*) FROM vehicle_prod WHERE fin LIKE '%00000' \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: vehicle_prod
   partitions: NULL
         type: index
possible_keys: NULL
          key: idx_vehicle_prod_fin
      key_len: 203
          ref: NULL
         rows: 3182812
     filtered: 11.11
        Extra: Using where; Using index
1 row in set, 1 warning (0.00 sec)

其中:

  • id select_id The SELECT identifier
  • select_type None The SELECT type
  • table table_name The table for the output row
  • partitions partitions The matching partitions
  • type access_type The join type
  • possible_keys possible_keys The possible indexes to choose
  • key key The index actually chosen
  • key_len key_length The length of the chosen key
  • ref ref The columns compared to the index
  • rows rows Estimate of rows to be examined
  • filtered filtered Percentage of rows filtered by table condition
  • Extra None Additional information


  1. https://dev.mysql.com/doc/refman/8.0/en/explain-output.html