如何在四个表之间应用 MySQL 中的左连接

Question

SELECT * FROM
  mtc_employee_master EB,
  mtc_employee_education_master EE,
  mtc_employee_experience_master EEXP,
  mtc_employee_salary_master ES 
WHERE
  EB.id=16 AND 
  EE.emp_tbl_id=EB.id AND 
  EEXP.emp_tbl_id=EB.id AND 
  ES.emp_tbl_id=EB.id

如果所有 table 中的数据都可用，则此方法工作正常。我想像大师一样从 mtc_employee_master 获取记录 table。

我成功地用下面的查询连接了两个 tables-

SELECT * FROM 
  mtc_employee_master EB 
LEFT JOIN 
  mtc_employee_education_master EE
ON
  EB.`id` = EE.`emp_tbl_id` 
WHERE
  EB.id=16

Answer 1

试试这个：

  SELECT * FROM mtc_employee_master EB
  left join mtc_employee_education_master EE on EE.emp_tbl_id=EB.id
  left join mtc_employee_experience_master EEXP on  EEXP.emp_tbl_id=EB.id 
  left join mtc_employee_salary_master ES on ES.emp_tbl_id =EB.id
  WHERE EB.id=16

Answer 2

这样做（已编辑）：

 SELECT EB.*
 FROM mtc_employee_master EB left join 
 (SELECT EE.id var FROM mtc_employee_education_master EE 
  join  mtc_employee_experience_master EEXP on EE.id=EEXP.id
  join mtc_employee_salary_master ES 
  on ES.id=EEXP.id) temp
  on EB.id= temp.var
 where  EB.id=16;

Answer 3

SELECT * FROM
  mtc_employee_master EB,
  mtc_employee_education_master EE,
  mtc_employee_experience_master EEXP,
  mtc_employee_salary_master ES 
WHERE
  EB.id=16 AND 
  IFNULL(EE.emp_tbl_id,0)IN(EB.id,0) AND 
  IFNULL(EEXP.emp_tbl_id,0)IN(EB.id,0) AND 
  IFNULL(ES.emp_tbl_id,0)IN(EB.id,0)

如何在四个表之间应用 MySQL 中的左连接

How to apply left join in MySQL between four tables

sql

left-join