mysql 将 2 行分组为 1，行之间只有一个不同的值

Question

I currently have this query:

SELECT Club_Name, SUM(Data_km) AS km, Type_id
FROM Data
INNER JOIN Clubs ON Data.Data_Club = Clubs.Club_id
INNER JOIN Types ON Clubs.Club_Type = Types.Type_id
WHERE Club_isActive = 1
GROUP BY Club_Name, Type_id

which gives me this table:

club_name	km	type
A	10	1
A	15	2
B	80	1
B	34	2
C	36	1

And I'm trying to achieve:

club_name	type 1 km	type 2 km
A	10	15
B	80	34
C	36

not all clubs will have a type 2. How do I rewrite the query to achieve the reorganization?

Answer 1

You can use conditional aggregation:

SELECT Club_Name, 
       SUM(CASE WHEN Type_id = 1 THEN Data_km END) as km_1,
       SUM(CASE WHEN Type_id = 2 THEN Data_km END) as km_2
FROM Data d JOIN
     Clubs c
     ON d.Data_Club = c.Club_id JOIN
     Types t
     ON c.Club_Type = t.Type_id
WHERE Club_isActive = 1
GROUP BY Club_Name;