How to retrieve multiple rows from stored procedure in MySQL? - mysql

Question

Am trying to fetch out a field through stored procedure and I used following query. I aimed at fetching out multiple rows, but it executes the result successfully only when a single row exists. Or else it returns an error as I mentioned below.
MySQL Query
DELIMITER ;;
DROP PROCEDURE IF EXISTS Sample1;;
CREATE PROCEDURE Sample1(IN lft1 INT, IN rgt1 INT, OUT emp1 VARCHAR(20))
BEGIN
SELECT p.emp INTO emp1
FROM personnel p
WHERE p.lft > lft1
AND p.rgt < rgt1
LIMIT 10;
END;;
CALL Sample1(1, 10, #emp);;
SELECT #emp;
Error Message
MySQL said: Documentation
#1172 - Result consisted of more than one row
NOTE
Sample1 - procedure name
emp - selected field from table personnel
lft - use to check the condition, it is also one of the field of table personnel
personnel - table name

Answer 1

The error is not in your procedure. The error is in your query - it returns more then one row, but you cannot set multiple result into scalar value 'emp1'.
You should limit your query so that it returns one row.
How to retreive multiple rows from stored procedure in mysql?
Plan A: Fill another table, it may be a temporary table.
Plan B: Just execute your SELECT statement without INTO clause from the procedure; then you could read data-set from the application (c#, PHP+mysqli,...)
Plan C: Do not use the procedure, just execute the SELECT query.

Answer 2

Just had the same question. After a little research I found a solution in the official MySQL documentation:
Calling Stored Procedures with Statement Objects
It requires MySQL 5.5.3 or higher.
In contrast to the inital stored procedure from #Bala.C it doesn't use an out parameter.
CREATE PROCEDURE get_data ()
BEGIN
SELECT Code, Name, Population, Continent
FROM Country
WHERE Continent = 'Oceania'
AND Population < 10000;
SELECT Code, Name, Population, Continent
FROM Country
WHERE Continent = 'Europe'
AND Population < 10000;
SELECT Code, Name, Population, Continent
FROM Country
WHERE Continent = 'North America'
AND Population < 10000;
END;

Answer 3

You can use a cursor in MySQL.
CREATE PROCEDURE Sample1(IN lft1 INT,IN rgt1 INT, OUT emp1 VARCHAR(20))
BEGIN
DECLARE p_emp INT;
DECLARE cur_emp CURSOR FOR
SELECT p.emp
FROM personnell p
WHERE p.lft > lft1
and p.rgt < rgt1
LIMIT 10;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET noMoreRow = 0;
OPEN cur_emp;
LOOPROWS: LOOP
IF noMoreRow = 0 THEN
CLOSE cur_emp;
LEAVE LOOPROWS;
END IF;
FETCH cur_emp INTO p_emp;
SELECT p_emp;
END LOOP;
END;;