how to reuse the resultset in mysql query - mysql

Question

I have result set like this after executing "select * from temp"
id | Month | value1 | value2 |
------------------------------
1 | Apr | 100 | 150
2 | May | 50 | 75
3 | Jan | 50 | 75
5 | Feb | 50 | 75
6 | mar | 50 | 75
I want to change it to column to rows like pivot table.
i used case when statement to change it.
select
'value1' as Field,
SUM(CASE
WHEN dc.month = 'January' THEN dc.value1
ELSE ''
END) AS January,
SUM(CASE
WHEN dc.month = 'February' THEN dc.value1
ELSE ''
END) AS February,
SUM(CASE
WHEN dc.month = 'March' THEN dc.value1
ELSE ''
END) AS March
SUM(CASE
WHEN dc.month = 'April' THEN dc.value1
ELSE ''
END) AS April,
SUM(CASE
WHEN dc.month = 'May' THEN dc.value1
ELSE ''
END) AS May
from
(select
* from
temp)dc
Field | Jan | Feb | Mar | Apr | May
-------------------------------------
Value1 | 50 | 50 | 50 | 100 | 50
I want to get same result set for value2 in same query without using UNION. Because temp table has lot of data's.
Field | Jan | Feb | Mar | Apr | May
-------------------------------------
Value1 | 50 | 50 | 50 | 100 | 50
Value1 | 75 | 75 | 75 | 150 | 75

Answer 1

This solution uses a union, but only to create "fake" rows to represent each value* column, and then joins and groups by those rows:
SELECT
`field`,
SUM(CASE
WHEN dc.month = 'Jan' THEN
CASE `field`
WHEN 'value1' THEN dc.value1
WHEN 'value2' THEN dc.value2
END
ELSE ''
END) AS January,
SUM(CASE
WHEN dc.month = 'Feb' THEN
CASE `field`
WHEN 'value1' THEN dc.value1
WHEN 'value2' THEN dc.value2
END
ELSE ''
END) AS February,
SUM(CASE
WHEN dc.month = 'Mar' THEN
CASE `field`
WHEN 'value1' THEN dc.value1
WHEN 'value2' THEN dc.value2
END
ELSE ''
END) AS March,
SUM(CASE
WHEN dc.month = 'Apr' THEN
CASE `field`
WHEN 'value1' THEN dc.value1
WHEN 'value2' THEN dc.value2
END
ELSE ''
END) AS April,
SUM(CASE
WHEN dc.month = 'May' THEN
CASE `field`
WHEN 'value1' THEN dc.value1
WHEN 'value2' THEN dc.value2
END
ELSE ''
END) AS May
FROM
(SELECT
* FROM temp
)dc
INNER JOIN (
SELECT 'value1' AS `field`
UNION SELECT 'value2'
) AS value_columns
GROUP BY `field`

Answer 2

If its just 2 colums i.e. value1 and value2 then you can use UNION as DEMO
select
'value1' as Field,
SUM(
CASE
WHEN dc.month = 'Jan' THEN dc.value1
ELSE ''
END) AS January,
SUM(
CASE
WHEN dc.month = 'Feb' THEN dc.value1
ELSE ''
END) AS February,
SUM(
CASE
WHEN dc.month = 'Mar' THEN dc.value1
ELSE ''
END) AS March,
SUM(
CASE
WHEN dc.month = 'Apr' THEN dc.value1
ELSE ''
END) AS April,
SUM(
CASE
WHEN dc.month = 'May' THEN dc.value1
ELSE ''
END)AS May
from
temp dc
UNION
select
'value2' as Field,
SUM(
CASE
WHEN dc.month = 'Jan' THEN dc.value2
ELSE ''
END) AS January,
SUM(
CASE
WHEN dc.month = 'Feb' THEN dc.value2
ELSE ''
END) AS February,
SUM(
CASE
WHEN dc.month = 'Mar' THEN dc.value2
ELSE ''
END) AS March,
SUM(
CASE
WHEN dc.month = 'Apr' THEN dc.value2
ELSE ''
END) AS April,
SUM(
CASE
WHEN dc.month = 'May' THEN dc.value2
ELSE ''
END)AS May
from temp dc