The Explain tab displays the information as a grid:
Column
|
Description
|
id | The SELECT identifier. This is the sequential number of the SELECT within the query. |
select_type | The type of SELECT, which can be SIMPLE, PRIMARY, UNION, DEPENDENT UNION, UNION RESULT, SUBQUERY, DEPENDENT SUBQUERY, DERIVED, UNCACHEABLE SUBQUERY or UNCACHEABLE UNION. |
table | The table to which the row of output refers. |
type | The join type. |
possible_keys | The possible_keys column indicates which indexes MySQL can choose from use to find the rows in this table. |
key | The key column indicates the key (index) that MySQL actually decided to use. |
key_len |
The key_len column indicates the length of the key that MySQL decided to use. |
ref |
The ref column shows which columns or constants are compared to the index named in the key column to select rows from the table. |
rows |
The rows column indicates the number of rows MySQL believes it must examine to execute the query. |
filtered |
The filtered column indicates an estimated percentage of table rows that will be filtered by the table condition. |
Extra |
This column contains additional information about how MySQL resolves the query. |