mysql> create table t1(a int primary key);
Query OK, 0 rows affected (0.11 sec)

mysql> explain select * from t1 where a = 1 and a = 2;
+-------------------+-------+------+------------------------------------------+
| id                | count | task | operator info                            |
+-------------------+-------+------+------------------------------------------+
| TableReader_6     | 0.00  | root | data:TableScan_5                         |
| └─TableScan_5     | 0.00  | cop  | table:t1, keep order:false, stats:pseudo |
+-------------------+-------+------+------------------------------------------+
2 rows in set (0.00 sec)

mysql> analyze table t1;
Query OK, 0 rows affected (0.00 sec)

mysql> explain select * from t1 where a = 1 and a = 2;
+-------------------+-------+------+------------------------------------------+
| id                | count | task | operator info                            |
+-------------------+-------+------+------------------------------------------+
| TableReader_6     | 0.00  | root | data:TableScan_5                         |
| └─TableScan_5     | 0.00  | cop  | table:t1, keep order:false, stats:pseudo |
+-------------------+-------+------+------------------------------------------+
2 rows in set (0.00 sec)

mysql> insert into t1 values(1);
Query OK, 1 row affected (0.00 sec)

mysql> explain select * from t1 where a = 1 and a = 2;
+-------------------+-------+------+------------------------------------------+
| id                | count | task | operator info                            |
+-------------------+-------+------+------------------------------------------+
| TableReader_6     | 0.00  | root | data:TableScan_5                         |
| └─TableScan_5     | 0.00  | cop  | table:t1, keep order:false, stats:pseudo |
+-------------------+-------+------+------------------------------------------+
2 rows in set (0.00 sec)

mysql> analyze table t1;
Query OK, 0 rows affected (0.01 sec)

mysql> explain select * from t1 where a = 1 and a = 2;
+-------------------+-------+------+----------------------------+
| id                | count | task | operator info              |
+-------------------+-------+------+----------------------------+
| TableReader_6     | 0.00  | root | data:TableScan_5           |
| └─TableScan_5     | 0.00  | cop  | table:t1, keep order:false |
+-------------------+-------+------+----------------------------+
2 rows in set (0.00 sec)