SQL＆＃34;重用＆＃34; WITH子句的结果？

Question

我有一个类似这样的查询：

;with Dataset1 as (SELECT columnA, columnB, SUM(columnC) as columnC  FROM Table1 GROUP BY columnA, columnB )

SELECT
    (SELECT columnC FROM Dataset1 WHERE columnA = '1' and columnB='2') as Result1,
    (SELECT columnC FROM Dataset1 WHERE columnA = '2' and columnB='3') as Result2,
    (SELECT columnC FROM Dataset1 WHERE columnA = '3' and columnB='4') as Result3,
...

我想知道的是，Dataset1是否在内存中被选中并重复使用每个select子句，或者SQL每次都会获取它？如果是这样的话，这看起来真的很浪费，我该怎么做才能优化呢？