如何在 mysql 的存储过程中将表名作为参数传递？

Question

I am trying to implement the below query in a stored procedure.

SELECT d.empno, d.fecthIdId, c.empno
FROM MyDatabase.myTable  a
JOIN MyDatabase.myTable b ON a.id = b.xid 
JOIN MyDatabase.Table2 c ON b.Id = cId 
JOIN MyDatabase.Table3 d ON a.bid = d.cid AND d.empId = _empId

Stored Procedure:

DELIMITER $$
CREATE  PROCEDURE `TestSP`(_empId INT,   _myTable VARCHAR(50))
BEGIN

SET @mysql.SQL
= CONCAT('SELECT d.empno, d.fecthIdId, c.empno
FROM MyDatabase.',_myTable,'  a
JOIN MyDatabase.',_myTable,'  b ON a.id = b.xid 
JOIN MyDatabase.Table2 c ON b.Id = cId 
JOIN MyDatabase.Table3 d ON a.bid = d.cid AND d.empId = _empId');

PREPARE dynamicQuery FROM @mysql.SQL;
EXECUTE dynamicQuery;
DEALLOCATE PREPARE dynamicQuery;

END$$
DELIMITER ;

Procedure Call:

call TestSP(10, 'myTable');

Error:

  Error Code: 1113. A table must have at least 1 column

I'm not sure what's wrong with the code. Thanks for your help.

Answer 1

You'd debug your code.

CREATE  PROCEDURE `TestSP`(_empId INT,   _myTable VARCHAR(50))
BEGIN

SET @mysql.SQL
= CONCAT('SELECT d.empno, d.fecthIdId, c.empno
FROM MyDatabase.',_myTable,'  a
JOIN MyDatabase.',_myTable,'  b ON a.id = b.xid 
JOIN MyDatabase.Table2 c ON b.Id = cId 
JOIN MyDatabase.Table3 d ON a.bid = d.cid AND d.empId = _empId');
/*
PREPARE dynamicQuery FROM @mysql.SQL;
EXECUTE dynamicQuery;
DEALLOCATE PREPARE dynamicQuery;
*/
SELECT @mysql.SQL `built SQL code`;
END

call TestSP(10, 'myTable');

built SQL code
SELECT d.empno, d.fecthIdId, c.empno FROM MyDatabase.myTable a JOIN MyDatabase.myTable b ON a.id = b.xid JOIN MyDatabase.Table2 c ON b.Id = cId JOIN MyDatabase.Table3 d ON a.bid = d.cid AND d.empId = _empId

fiddle

Now copypaste this code into your CLI and try to execute it.