sql leaning 2

explain.md

Sql

explain select * from vanrating_latest_backup where rating=3 or rating=4;

Result

+------+-------------+-------------------------+------+---------------+------+---------+------+------+-------------+
| id   | select_type | table                   | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+------+-------------+-------------------------+------+---------------+------+---------+------+------+-------------+
|    1 | SIMPLE      | vanrating_latest_backup | ALL  | NULL          | NULL | NULL    | NULL |   12 | Using where |
+------+-------------+-------------------------+------+---------------+------+---------+------+------+-------------+

Importance

type

1. Ref (Best)
2. ALL (Worst)

possible_keys

That the keys will be consider as index of mysql engine

key

Key for indexing

Rows

How many row has been read