如果行中的其他值满足特定条件，则使用 SQL 聚合数据

Question

I'm pretty new to SQL and am trying to figure out if there's a way to aggregate the date into new column. For instance, below is a sample set of date. I want to take all the type '2' and create new columns

Mem   Balance  Type  New
 1     2500     2    0
 2     722      66   1
 3     9422      1   0
 4     122       2   1
 5     788      66   1

So instead of having it like above, it would be like

Mem   Type2Balance  Type66Balance   Type2New    Type66New
1       2622            0            1             0
2         0            1510          0             2

Is there a way to do this in SQL? I thought maybe using IF statements within a case statement? I'm not asking for it to be done for me, more of looking for specifics that I can read about to make this happen. Thank you!

Answer 1

It seems like you want:

select
    case when type = 2 then sum(balance) else 0 end type2balance,
    case when type = 66 then sum(balance) else 0 end type66balance,
    case when type = 2 then sum(new) else 0 end type2new,
    case when type = 66 then sum(new) else 0 end type66new
from mytable
where type in (2, 66)
group by type

I am not sure what logic you want for column Mem in the resulset. It that's just a row number, then:

select
    row_number() over(order by type) mem,
    case when type = 2 then sum(balance) else 0 end type2balance,
    case when type = 66 then sum(balance) else 0 end type66balance,
    case when type = 2 then sum(new) else 0 end type2new,
    case when type = 66 then sum(new) else 0 end type66new
from mytable
where type in (2, 66)
group by type

We could put the conditional expression on type inside the aggregate function, but it does not really make sense since you are grouping by type already. In that case, that would be:

select
    row_number() over(order by type) mem,
    sum(case when type = 2 then balance else 0 end) type2balance,
    sum(case when type = 66 then balance else 0 end) type66balance,
    sum(case when type = 2 then new else 0 end) type2new,
    sum(case when type = 66 then new else 0 end) type66new
from mytable
where type in (2, 66)
group by type

Answer 2

With conditional aggregation:

select min(mem) mem,
  sum(case when type = 2 then balance else 0 end) Type2Balance,
  sum(case when type = 66 then balance else 0 end) Type66Balance,
  sum(case when type = 2 then new else 0 end) Type2New,
  sum(case when type = 66 then new else 0 end) Type66New
from tablename
where type in (2, 66)
group by type

See the demo .
Results:

| mem | Type2Balance | Type66Balance | Type2New | Type66New |
| --- | ------------ | ------------- | -------- | --------- |
| 1   | 2622         | 0             | 1        | 0         |
| 2   | 0            | 1510          | 0        | 2         |