Error when calling a SP from another one - mysql

Question

I have created the following MySQL SP successfully..
CREATE DEFINER=`root`#`%` PROCEDURE `Common_Proc_Create_NewId`
(
TableName VARCHAR(250),
ColumnName VARCHAR(150),
OUT ReturnId BIGINT
)
BEGIN
DECLARE varb BIGINT;
SET #NewId:= CONCAT('SELECT (IFNULL(MAX(', ColumnName, '), 0) + 1) INTO ', varb, ' FROM ', TableName);
PREPARE Stmnt FROM #NewId;
EXECUTE Stmnt;
DEALLOCATE PREPARE Stmnt;
SET ReturnId = varb;
END$$
But when this was called from another SP I got the following error:
Error Code: 1064 You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near 'NULL' at line 1
Calling SP
CREATE DEFINER=`root`#`%` PROCEDURE `Masters_Proc_Create_BranchType`(
BranchTypName VARCHAR(100)
)
BEGIN
CALL Common_Proc_Create_NewId('Masters_BranchType', 'BranchTypeId', #Id);
INSERT INTO Masters_BranchType (BranchTypeId, BranchTypeName) VALUES (#Id, BranchTypName);
SELECT #Id;
END$$

Answer 1

In your stored procedure Common_Proc_Create_NewId the part into varb was causing the issue and think it's not allowed that way in a prepared statement (not sure though). Instead the way you are doing, try like below and it works fine (a sample code included)
delimiter //
CREATE PROCEDURE dynamic1(IN tbl VARCHAR(64), IN col VARCHAR(64), OUT ret int)
BEGIN
SET #s = CONCAT('SELECT #i := (IFNULL(MAX(', col, '), 0) + 1) FROM ', tbl);
PREPARE stmt FROM #s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
set ret = #i;
END
//
delimiter ;
call dynamic1('test1','col',#id);
select #id;