MariaDB [db]> SELECT * from jobseeker_account WHERE email_address = 0;
+----+----------------+--------------------------------+------------------------------------------+------------+--------------+--------------------------------------------------------------+-----------+-------------+---------------------+---------------------+------------------+--------+
| id | jobseeker_code | email_address | email_token | code_token | email_verify | password | google_id | facebook_id | date_created | last_login | last_change_pass | status |
+----+----------------+--------------------------------+------------------------------------------+------------+--------------+--------------------------------------------------------------+-----------+-------------+---------------------+---------------------+------------------+--------+
| 1 | APP052000001 | user@gmail.com | 4d517de609a97afae45aee04d4862e8a7c195805 | 678503 | 0 | $2y$10$0Ug1iGPsBqoy5p7YjwOx3uQwQLM6S5hyYy8e2QX9yYwlqsNNnoHJS | NULL | NULL | 2020-05-14 16:25:50 | 2020-05-14 16:25:50 | NULL | 1 |
| 2 | APP052000002 | user@gmail1.com | f5ce9b3b545019c71a0846e13c10a1c8a5edb3bd | 397097 | 0 | $2y$10$CGXrDVMUKrtreLgQ0gkEp.UNBa8ogtJ6SWhxPjUQEQ7a1GxhPBg1W | NULL | NULL | 2020-05-14 19:36:31 | 2020-05-14 19:36:31 | NULL | 1 |
+----+----------------+--------------------------------+------------------------------------------+------------+--------------+--------------------------------------------------------------+-----------+-------------+---------------------+---------------------+------------------+--------+
2 rows in set, 2 warnings (0.001 sec)
即使电子邮件地址列中没有 0 值，我也得到结果
当此条件：
email_address = 0
被评估，发生的情况是将电子邮件隐式转换为整数，以便相等的两个部分具有相同的数据类型。
无法转换为整数的值(如user@gmail.com(的转换结果为0。
因此，条件返回电子邮件的此类值的TRUE。
如果有像123user@gmail.com这样的电子邮件，它将被转换为123并且您将无法在结果中得到它。
有关表达式中类型转换的所有内容都在此处说明：
表达式计算中的类型转换