mysql - mysql 在开关构造中使用替代名称

Question

我尝试使用下面的代码进行选择

Select `admin`.`admin_id`, `admin`.`email` AS `admin_email`, IF(customer.email IS NOT NULL OR admin_email IS NOT NULL, 'Subscribed', 'Unsubscribed') AS `field_name`, (...Something else) from admin, customer, (...Something else);

然后得到错误#1054 - Unknown column 'admin_email' in 'field list'

标签： mysqlmysql-error-1054

Answer 1

你不能在 if 语句中使用别名，所以

选择admin。admin_id, admin. emailAS admin_email, IF(customer.email IS NOT NULL OR admin.email IS NOT NULL, 'Subscribed', 'Unsubscribed') AS field_name, (...Something else) from admin, customer, (...Something else);