Hierarchical Query in MySQL. (connect by equivalent for MySQL)

问题

I have three fields in a table that define a hierarchical relationship present in a MySQL database.

Table Name : tb_corp
--------------------------------------------
  comp_code  | incharge_comp_Code | mngr_emp_no

     A       |                    |    111
--------------------------------------------
     B       |          A         |  
--------------------------------------------
     C       |          B         |    
--------------------------------------------

How do I write a query to obtain all the comp_code that mngr_emp_no = 111 is in charge. According to the table above, 111 is in charge of three companies(A, B, and C). The reason is that A company is in charge of B company and B company is in charge of C company as a result A is also in charge of C company. (A -> B) (B -> C) == (A -> C)

回答1:

There is no native hierarchical query support in MySQL.

For a finite number of levels to be traversed, we can write queries that get result for each level, and combine the results with a UNION ALL operator.

Or, we can write a MySQL stored program (procedure) for a more recursive approach.

As an example of approach using a native SQL query:

 SELECT t0.comp_code
   FROM tb_corp t0
  WHERE t0.mgr_emp_no = 111

 UNION ALL

SELECT t1.comp_code
  FROM tb_corp t0
  JOIN tb_corp t1 ON t1.incharge_comp_code = t0.comp_code
 WHERE t0.mgr_emp_no = 111

 UNION ALL

SELECT t2.comp_code
  FROM tb_corp t0
  JOIN tb_corp t1 ON t1.incharge_comp_code = t0.comp_code
  JOIN tb_corp t2 ON t2.incharge_comp_code = t1.comp_code
 WHERE t0.mgr_emp_no = 111

 UNION ALL

SELECT t3.comp_code
  FROM tb_corp t0
  JOIN tb_corp t1 ON t1.incharge_comp_code = t0.comp_code
  JOIN tb_corp t2 ON t2.incharge_comp_code = t1.comp_code
  JOIN tb_corp t3 ON t3.incharge_comp_code = t2.comp_code
 WHERE t0.mgr_emp_no = 111

etc. This approach can be extended to t4, t5, t6, ... down to some (reasonable) finite number of levels.

For a more recursive approach, a MySQL stored program (PROCEDURE) can be written.

来源：https://stackoverflow.com/questions/42264913/hierarchical-query-in-mysql-connect-by-equivalent-for-mysql

标签

mysql

mariadb