Retrieving more than one rows in a stored procedure

Question

I need to perform a full table level scan as it should be supposed to retrieve more than one rows based on the User ID.

Since I used to get sqlMessage stating 'Subquery returns more than 1 row'.

{ Error: ER_SUBQUERY_NO_1_ROW: Subquery returns more than 1 row
  ...
  code: 'ER_SUBQUERY_NO_1_ROW',
  errno: 1242,
  sqlMessage: 'Subquery returns more than 1 row',
  sqlState: '21000',
  index: 0,
  sql: 'CALL GetLocationTag(1)' }

Here is the call made to the GetLocationTag() code

DELIMITER $$

CREATE
    DEFINER = `root`@`localhost`
    PROCEDURE `someDB`.`GetLocationTag`(IN `UserId` BIGINT)
    LANGUAGE SQL
    DETERMINISTIC
    READS SQL DATA 
    SQL SECURITY DEFINER 
    COMMENT 'Retrieves Multiple Stored Location Tags, Address, Location, etc. based on User_ID'
    BEGIN
        DECLARE flag INT(11);
        DECLARE locRecord VARCHAR(255);

            IF EXISTS (SELECT * FROM `location_map` WHERE `user_id` = User_Id ) THEN  
                BEGIN
                    SELECT * INTO locRecord FROM `location_map` WHERE `user_id` = User_Id;
                    SET flag = 1;
                END;            
            ELSE
                SET flag = 0;
                SET locRecord = 0;
            END IF;

        SELECT locRecord, flag;
    END$$

DELIMITER ;

For the below query,

SELECT * INTO locRecord FROM `location_map` WHERE `user_id` = User_Id;

How am I need to retrieve all the rows in the form of arrays & store it into variable OR How am I suppose to code such that error message should need to be resolved?

Answer 1

Use a view to store your fetched data instead of a variable

DELIMITER $$

CREATE
    DEFINER = `root`@`localhost`
    PROCEDURE `someDB`.`GetLocationTag`(IN `User_Id` BIGINT)
    LANGUAGE SQL
    DETERMINISTIC
    MODIFIES SQL DATA
    SQL SECURITY DEFINER
    COMMENT 'Retrieves Multiple Stored Location Tags, Address, Location, etc. based on User_ID'
    BEGIN
        DECLARE flag INT(11);
        DECLARE locRecord VARCHAR(255);

            IF EXISTS (SELECT * FROM `location_map` WHERE `user_id` = User_Id ) THEN  
                BEGIN
                    SET @viewQry = CONCAT('CREATE OR REPLACE VIEW `someDB`.`temp` as SELECT *, 1 as flag FROM `location_map` WHERE `user_id` = ',User_Id,';');
                    PREPARE stmt FROM @viewQry; 
                    EXECUTE stmt; 
                    DEALLOCATE PREPARE stmt;
                    SELECT * FROM temp;
                END;            
            ELSE
                SELECT 0 AS locRecord, 0 AS flag;
            END IF;
    END$$

DELIMITER ;