如何在MySql中加入多个条件表

Question

我有perf_component_valuation表：

然后我加入它：

SELECT CONCAT(ee.first_name,' ',ee.last_name) as valuated_name,CONCAT(ee.first_name,' ',ee.last_name) as valuator_name from emp_employee as ee 
left join perf_component_valuation as pcv on pcv.valuator=ee.employee_id
WHERE pcv.phc_id =49;

试试这个：

SELECT CONCAT(ee.first_name,' ',ee.last_name) as valuated_name,CONCAT(ee.first_name,' ',ee.last_name) as valuator_name from emp_employee as ee 
left join perf_component_valuation pcv on pcv.valuator=ee.employee_id
left join perf_component_valuation pcv2 on pcv2.valuated=ee.employee_id
WHERE pcv.phc_id =49;

但它只给我一个估价师名称，而不是估价。这是结果：



我想要的结果是：

valuated_name || valuator_name
______________________________
Adni          || Arli Ramdhani
Adni          || Mohammad Aldo

我怎样才能给出另一个条件？

Answer 1

尝试两次加入emp_employee

SELECT CONCAT(valuated_ee.first_name,' ',valuated_ee.last_name) as valuated_name,CONCAT(valuator_ee.first_name,' ',valuator_ee.last_name) as valuator_name 
from perf_component_valuation as pcv
left join emp_employee as valuated_ee on pcv.valuated=valuated_ee.employee_id
left join emp_employee as valuator_ee on pcv.valuator=valuator_ee.employee_id
WHERE pcv.phc_id =49;

Answer 2

你使用了一个相同的别名ee，试试这个;）

SELECT CONCAT(pcv.first_name,' ',pcv.last_name) as valuated_name,CONCAT(ee.first_name,' ',ee.last_name) as valuator_name from emp_employee as ee 
left join perf_component_valuation as pcv on pcv.valuator=ee.employee_id
WHERE pcv.phc_id =49;