Question

我有一个非常恶心的查询，运行起来有点慢：

SELECT TOP 10 d.AccountID, COUNT(mp.PhoneTypeID) AS Num_Phones,
sum(case when mp.PhoneTypeID = 1 then 1 else 0 end) AS type1,
sum(case when mp.PhoneTypeID = 2 then 1 else 0 end) AS type2,
sum(case when mp.PhoneTypeID = 3 then 1 else 0 end) AS type3,
sum(case when mp.PhoneTypeID = 4 then 1 else 0 end) AS type4,
sum(case when mp.PhoneTypeID = 5 then 1 else 0 end) AS type5,
sum(case when mp.PhoneTypeID = 6 then 1 else 0 end) AS type6,
sum(case when mp.PhoneTypeID = 7 then 1 else 0 end) AS type7,
sum(case when mp.PhoneTypeID = 8 then 1 else 0 end) AS type8,
sum(case when mp.PhoneTypeID = 9 then 1 else 0 end) AS type9,
sum(case when mp.PhoneTypeID = 10 then 1 else 0 end) AS type10,
sum(case when mp.PhoneTypeID = 11 then 1 else 0 end) AS type11,
sum(case when mp.PhoneTypeID = 12 then 1 else 0 end) AS type12,
sum(case when mp.PhoneTypeID = 13 then 1 else 0 end) AS type13,
sum(case when mp.PhoneTypeID = 14 then 1 else 0 end) AS type14,
sum(case when mp.PhoneTypeID = 15 then 1 else 0 end) AS type15,
sum(case when mp.PhoneTypeID = 16 then 1 else 0 end) AS type16,
sum(case when mp.PhoneTypeID = 17 then 1 else 0 end) AS type17
INTO #phoneshit
FROM #days d
INNER JOIN note.phone np on d.AccountID = np.AccountID INNER JOIN main.phone 
mp ON np.PhoneID = mp.PhoneID
GROUP BY d.AccountID

我想不出任何其他方法将电话类型过滤成这样的新列，更不用说更快的方法了。有人知道吗？在这种情况下最好的方法是什么？

Answer 1

对于性能问题，您应该考虑在AccountID临时表的列#days上添加索引，连接应该快得多。

对于“可读性”，您可以在PIVOT上PhoneTypeID

;with
x as (
    select AccountID, PhoneTypeID
    from #days d
    join note.phone np on d.AccountID = np.AccountID
    join main.phone mp ON np.PhoneID = mp.PhoneID
),
p as (
    select *
    from x
    pivot ( count(PhoneTypeID) for PhoneTypeID in ([1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17])) p
),
n as (
    select AccountID, COUNT(PhoneTypeID) Num_Phones
    from x
    group by AccountID
)   
select p.AccountID, n.Num_Phones, [1] type1, [2] type2, [3] type3, [4] type4, [5] type5, [6] type6, [7] type7 , [8] type8, [9] type9, [10] type10, [11] type11, [12] type12, [13] type13, [14] type14, [15] type15, [16] type16, [17] type17
into #phoneshit
from p
join n on p.AccountID = n.AccountID

有17个子查询用例语句，还有更好的方法吗？

1 个答案: