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percona-toolkit/t/pt-visual-explain/samples/impossible_on_condition.sql

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SQL

explain select * from t2 LEFT JOIN t on t2.id = t.id AND 1 = 0 WHERE t2.id = 1;
+------+-------------+-------+-------+---------------+------+---------+------+------+-------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+-------+-------+---------------+------+---------+------+------+-------------------------+
| 1 | SIMPLE | t | const | t_id | NULL | NULL | NULL | 0 | Impossible ON condition |
| 1 | SIMPLE | t2 | ALL | NULL | NULL | NULL | NULL | 1 | Using where |
+------+-------------+-------+-------+---------------+------+---------+------+------+-------------------------+