php - 为什么会出现此错误？语法错误或访问冲突 : 1066 Not unique table/alias: 'Employees'

Question

这是我的 SQL 查询:

SELECT Employees.employee_id AS `Employees__employee_id`, 
    Employees.designation_id AS `Employees__designation_id`, 
    Employees.first_name AS `Employees__first_name`, 
    Employees.last_name AS `Employees__last_name`, 
    Employees.address AS `Employees__address`, 
    Employees.contact_no AS `Employees__contact_no`, 
    Employees.joining_date AS `Employees__joining_date`, 
    Employees.username AS `Employees__username`, 
    Employees.password AS `Employees__password`, 
    Employees.basic_pay AS `Employees__basic_pay`, 
    Employees.create_date AS `Employees__create_date`, 
    Employees.status AS `Employees__status`, 
    Designations.designation_id AS `Designations__designation_id`, 
    Designations.designation_name AS `Designations__designation_name`, 
    Designations.description AS `Designations__description` 
FROM employees Employees 
INNER JOIN employees Employees 
    ON Employees.employee_id = (Employees.employee_id) 
INNER JOIN designations Designations 
    ON Designations.designation_id = (Employees.designation_id) 
LIMIT 20 OFFSET 0

我得到的错误是:

Error: SQLSTATE[42000]: Syntax error or access violation: 1066 Not unique table/alias: 'Employees'!

你能帮我做这件事吗？

Answer 1

不能对查询中的多个表使用相同的别名 (Employees)。在这里，您在 from 和 join 子句中都使用了它。只需在其中一个中使用不同的别名就可以了。