mysql version error in store procedure - mysql

Question

below is my query:
DELIMITER $$
DROP PROCEDURE IF EXISTS `UpdateDB_Base_Url`$$
CREATE PROCEDURE UpdateDB_Base_Url()
BEGIN
DECLARE #rownum INT DEFAULT 1;
DECLARE #tbname VARCHAR(50);
WHILE #rownum<105 DO
SET #tbname= SELECT CONCAT((SELECT dbname FROM temp_db WHERE rownum=#rownum),'.','core_config_data');
UPDATE #tbname t
SET t.`value` =CONCAT(SUBSTRING(`value`, 1,LOCATE('.' ,`value`)),'magapa.ns-staging.com.au')
WHERE t.`value` LIKE '%staging-php%';
SET #rownum=#rownum+1;
END WHILE;
END$$
DELIMITER ;
temp_db table has db names with row number upto 104 records. here i am trying to update a table by going through all dbs in my server and i am getting following error
Query: CREATE PROCEDURE UpdateDB_Base_Url() begin declare #rownum int default 1; declare #tbname varchar(50); while #rownum<105 do SET ...
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 '#rownum int default 1;
declare #tbname varchar(50);
while #rownum<105 do
SET #' at line 3
Can someone help me with this?
Thanks!

Answer 1

There are few issues with your code.
You need not qualify local variables with '#' symbol. They are for
user/session variables.
You can read output of an expression into a local variable using
select ... into. No explicit set and select are required.
You can't just update a table with table name read from a
variable, directly. You have to use Prepared Statement.
Change your code as below:
DELIMITER $$
DROP PROCEDURE IF EXISTS `UpdateDB_Base_Url` $$
CREATE PROCEDURE UpdateDB_Base_Url()
BEGIN
DECLARE _rownum INT DEFAULT 1;
DECLARE _tbname VARCHAR(50);
SET _rownum := 1;
WHILE _rownum < 105 DO
SELECT CONCAT( dbname, ',', 'core_config_data' )
INTO _tbname
FROM temp_db
WHERE rownum = _rownum;
SET #sql := CONCAT( 'UPDATE ', _tbname, ' t ' );
SET #sql := CONCAT( #sql, ' SET t.`value` = ' );
SET #sql := CONCAT( #sql, ' CONCAT( SUBSTRING( t.`value`, 1, ' );
SET #sql := CONCAT( #sql, ' LOCATE( \'.\', t.`value` ) )' );
SET #sql := CONCAT( #sql, ', \'magapa.ns-staging.com.au\' )';
SET #sql := CONCAT( #sql, ' WHERE t.`value` LIKE \'%staging-php%\'' );
PREPARE stmt FROM #sql;
EXECUTE stmt;
DROP PREPARE stmt;
SET _rownum := _rownum + 1;
END WHILE;
END;
$$
DELIMITER ;