i would like convert data from Table1 as you can see on first picture on data in Pivot_table. Is possible to do that in MySQL? Because the values of pivot table(A, B, C, D) are in varchar data format and i cannot use any aggregation function of MySQL like SUM or others.
Table1:
PK Name Subject Grade
-------------------------------------
1 Bob Math A
2 Bob History B
3 Bob Language C
4 Bob Biology D
5 Sue History C
6 Sue Math A
7 Sue Music A
8 Sue Geography C
Pivot_table:
Subject Bob Sue
-------------------------
Math A A
History B C
Language C
Biology D
Music A
Geography C
Thanks for your help
A static query (as far as only Bob and Sue are concerned) might look like this
SELECT subject,
MAX(CASE WHEN name = 'Bob' THEN grade END) `Bob`,
MAX(CASE WHEN name = 'Sue' THEN grade END) `Sue`
FROM table1
GROUP BY subject
Now to be able to account for other names use dynamic SQL like this
SET @sql = NULL;
SELECT GROUP_CONCAT(DISTINCT
CONCAT('MAX(CASE WHEN name = ''', name,
''' THEN grade END) `', name, '`'))
INTO @sql
FROM table1;
SET @sql = CONCAT('SELECT subject, ', @sql, '
FROM table1
GROUP BY subject');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
Output:
| SUBJECT | BOB | SUE | |-----------|--------|--------| | Biology | D | (null) | | Geography | (null) | C | | History | B | C | | Language | C | (null) | | Math | A | A | | Music | (null) | A |
Here is SQLFiddle demo
You can wrap it into a stored procedure to simplify things on the calling end
DELIMITER $$
CREATE PROCEDURE sp_grade_report()
BEGIN
SET @sql = NULL;
SELECT GROUP_CONCAT(DISTINCT
CONCAT('MAX(CASE WHEN name = ''', name,
''' THEN grade END) `', name, '`'))
INTO @sql
FROM table1;
SET @sql = CONCAT('SELECT subject, ', @sql, '
FROM table1
GROUP BY subject');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;
Sample usage:
CALL sp_grade_report();
Here is SQLFiddle demo
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With