“Linux:统计文本行数”与“MySQL explain”:页面之间的差异

来自WHY42
(页面间差异)
无编辑摘要
 
无编辑摘要
 
第1行: 第1行:
= 例子 =
<pre>
<pre>
hfli@CNhfli ~/Desktop/___ $ wc -l s.csv
mysql> explain SELECT COUNT(*) FROM vehicle_prod WHERE fin LIKE '%00000' \G
   213330 s.csv
*************************** 1. row ***************************
hfli@CNhfli ~/Desktop/___ $ wc -l s.csv | awk '{print $1}'
          id: 1
213330
   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)
</pre>
 
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


</pre>


[[Category:Linux/Unix]]
#https://dev.mysql.com/doc/refman/8.0/en/explain-output.html
[[Category:Datebase]]

2021年5月3日 (一) 10:18的版本

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