Please anyone help about my case in mysql query - mysql

Question

I have this data..
+------+--------------+------------+
+ id + position_id + name +
+------+--------------+------------+
+ 1 + 1 + name_1 +
+ 2 + 5 + name_2 +
+ 3 + 2 + name_3 +
+ 4 + 2 + name_4 +
+ 5 + 2 + name_5 +
+ 6 + 3 + name_6 +
+ 7 + 4 + name_7 +
+ 8 + 3 + name_8 +
+ 9 + 2 + name_9 +
+------+--------------+------------+
..then I want the the results is like
+--------------+-----------+----------+----------+-----------+
+ position_id + result1 + result2 + result3 + result4 +
+--------------+-----------+----------+----------+-----------+
+ 1 + name_1 + # + # + # +
+ 2 + name_3 + name_4 + name_5 + name_9 +
+ 3 + name_6 + name_8 + # + # +
+ 4 + name_7 + # + # + # +
+ 5 + name_2 + # + # + # +
+--------------+-----------+----------+----------+-----------+
I have some case for resulting data, this data is for my school reports. The data results must be dynamic following primary of position and if the result is empty will sowing #.
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Answer 1

If a fixed number of columns then you could do something like this:-
SELECT a.position_id,
COALESCE(MIN(a.name), '#') AS result1,
COALESCE(MIN(b.name), '#') AS result2,
COALESCE(MIN(c.name), '#') AS result3,
COALESCE(MIN(d.name), '#') AS result4
FROM some_table a
LEFT OUTER JOIN some_table b ON a.position_id = b.position_id AND a.id < b.id
LEFT OUTER JOIN some_table c ON a.position_id = c.position_id AND b.id < c.id
LEFT OUTER JOIN some_table d ON a.position_id = d.position_id AND c.id < d.id
GROUP BY a.position_id
With a variable number of columns it isn't going to be possible really without dynamically creating the SQL based on the number of columns, or doing something nasty with GROUP_CONCAT.
But this isn't likely to be efficient.
It would probably be better to do a query to get the first results and then sort out the formatting in the calling script.
EDIT
Time for some nasty code, and i still needs polishing!
First bit is a stored procedure. This gets the max number of columns (gets it slightly wrong, but should be easy to fix with a bit of effort, and works for now) and dynamically builds up the SQL to create a temp table with this number of columns, and then populates it.
DELIMITER ;;
CREATE DEFINER=CURRENT_USER PROCEDURE stored_procedure_name()
BEGIN
DECLARE sql1 TEXT;
DECLARE sql2 TEXT;
DECLARE sql3 TEXT;
SET ##group_concat_max_len = 32000;
SELECT
GROUP_CONCAT(CONCAT('MIN(a', (1 + units.iCnt + 10 * tens.iCnt), '.name) AS result', (1 + units.iCnt + 10 * tens.iCnt)) ORDER BY (1 + units.iCnt + 10 * tens.iCnt)),
GROUP_CONCAT(CONCAT('LEFT OUTER JOIN some_table a', (1 + units.iCnt + 10 * tens.iCnt), ' ON a', (units.iCnt + 10 * tens.iCnt), '.position_id = a', (1 + units.iCnt + 10 * tens.iCnt), '.position_id AND a', (units.iCnt + 10 * tens.iCnt), '.id < a', (1 + units.iCnt + 10 * tens.iCnt), '.id') ORDER BY (1 + units.iCnt + 10 * tens.iCnt) SEPARATOR ' '),
GROUP_CONCAT(CONCAT('result',(1 + units.iCnt + 10 * tens.iCnt), ' VARCHAR(255)') ORDER BY (1 + units.iCnt + 10 * tens.iCnt))
INTO sql1, sql2, sql3
FROM
(
SELECT MAX(count_name) as max_count_name
FROM
(
SELECT COUNT(name) as count_name
FROM some_table
GROUP BY position_id
) sub0
) sub1,
(SELECT 1 iCnt UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9 UNION SELECT 0) units,
(SELECT 1 iCnt UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9 UNION SELECT 0) tens
WHERE max_count_name >= (units.iCnt + 10 * tens.iCnt);
DROP TEMPORARY TABLE IF EXISTS temp1;
SET #sqlmain1 = CONCAT('CREATE TEMPORARY TABLE temp1(position_id INT, result0 VARCHAR(255), ', sql3, ')');
PREPARE stmt FROM #sqlmain1;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET #sqlmain2 = CONCAT('INSERT INTO temp1 SELECT a0.position_id, MIN(a0.name) AS result0,', sql1, ' FROM some_table a0 ', sql2, ' GROUP BY a0.position_id ');
PREPARE stmt FROM #sqlmain2;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END;;
DELIMITER ;
You can then execute this and then select from the resulting temp table. Note that both statements must be done in the same SQL session, otherwise the temp table will have disappeared by the time you do the select:-
CALL stored_procedure_name();
SELECT * FROM temp1
Hopefully you can pass these both to Jasper.