SQL-使用where子句的select中具有不同的总和级别

Question

I have 2 tables. One has the orginal amount that remains static. The second table has a list of partial amounts applied over time against the orginal amount in the first table.

DB Tables:

***memotable***
ID [primary, unique]
Amount (Orginal Amount)

***transtable***
ID [many IDs in transtable to single ID in memotable] 
AmountUsed (amount applied)
ApplyDate (date applied)

I would like to find, in a single select, the ID, amount used since last week (ApplyDate > 2011-04-21), amount used to date.

The only rows that should appear in the result is when an amount has been used since last week (ApplyDate > 2011-04-21).

I'm stuck on trying to get the sum for the amount used to date, since that needs to include AmountUsed values that are outside of when ApplyDate > 2011-04-21.

Answer 1

It is possible to avoid subselects in this case:

SELECT
  ID,
  AmountUsedSinceLastWeek = SUM(CASE WHEN ApplyDate > '4/21/2011' THEN AmountUsed END)
  AmountUsedToDate = SUM(AmountUsed)
FROM TransTable
GROUP BY ID

Answer 2

Since you want to limit it to rows that happened since last week, but also want to include the total to date, I think the most efficient method would be to use sub-selects...

SELECT
    lastWeek.ID,
    lastWeek.AmountUsedSinceLastWeek,
    toDate.AmountUsedToDate
FROM
(
    SELECT
        ID,
        SUM(AmountUsed) AS AmountUsedSinceLastWeek
    FROM TransTable
    WHERE ApplyDate > '4/21/2011'
    GROUP BY ID
) lastWeek JOIN
(
    SELECT
        ID,
        SUM(AmountUsed) AS AmountUsedToDate
    FROM TransTable
    GROUP BY ID
) toDate ON lastWeek.ID = toDate.ID