How to add rows that is grouped by a new group in mysql?

Question

Update: This is a different question to the previous one, when I use ROLLUP in this question, it will add a total row, but I only want a group C to combine group A and B, thus group C shows the subtotal of color X, Y and Z. No total row needed.

I have data like this

Group Color Money
A     X     100
A     X     300
A     Y     200
B     X     200
B     Y     300
B     Y     100
B     Z     110

I want to make a new Group C that contains A&B

Is there anyway to query out data in mysql like this?

Group Color SumMoney AvgMoney DataCount
A     X     400      200      2
A     Y     200      200      1
B     X     200      200      1
B     Y     400      200      2    
B     Z     110      110      1
C     X     600      200      3
C     Y     600      200      3
C     Z     110      110      1

I think UNION may solve the problem but it may also be slow and the syntax would be long(harder to maintain(not in this case)). Any suggestions? Thanks!

Answer 1

Use UNION ALL in MySQL:

SELECT
    g.`group`,
    g.color,
    sum(g.money) AS SumMoney,
    CAST(AVG(g.money) AS SIGNED) AS AvgMoney,
    COUNT(g.`group`) AS DataCount
FROM
    groups g
GROUP BY
    g.`group`,
    g.color

UNION ALL

SELECT
    'C',
    g.color,
    sum(g.money) AS SumMoney,
    CAST(AVG(g.money) AS SIGNED) AS AvgMoney,
    COUNT(g.`group`) AS DataCount
FROM
    groups g
GROUP BY
    g.color

Output is:

group | color | SumMoney | AvgMoney | DataCount
-----------------------------------------------
A     | X     |      400 |      200 |        2
A     | Y     |      200 |      200 |        1
B     | X     |      200 |      200 |        1
B     | Y     |      400 |      200 |        2
B     | Z     |      110 |      110 |        1
C     | X     |      600 |      200 |        3
C     | Y     |      600 |      200 |        3
C     | Z     |      110 |      110 |        1

Answer 2

select group,color,sum(money) as SumMoney ,avg(money) as AvgMoney,
       count(*) as DataCount from table_name group by group,color