MySQL explain

来自WHY42
Riguz留言 | 贡献2018年9月18日 (二) 09:16的版本
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