Ask a few super simple SQL statements:

lxyxhl

1. There is a table, name, quantity... already sorted in descending order.
Find the sum of the names of the first 20% of it.
Similar to:

select top 20 percent quantity from table name //This sentence is OK..
//The following will not work.
declare @departtotal int
select @departtotal = sum (select top 20 percent quantity from table name)

fanfan1980

--try

declare @departtotal int
select top 20 percent @departtotal=sum(number) from table name
select @departtotal

unkmass

Try:
declare @departtotal int
select @departtotal = sum(quantity) from (select top 20 percent quantity from table name) t

lxyxhl

fanfan1980I don't know why, what you asked for is the total..
unkmassOh, you can. After thinking for a while, I understand why a "t" is needed in the back

yzysjl

Learn

haigerrual

Try:
declare @departtotal int
select @departtotal = sum(quantity) from (select top 20 percent quantity from table name) t

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Leave a mark
I would like to ask what is the difference between @departtotal = sum(quantity) and removing sum. Because you come from a table t that only has quantity, then you select the top 20% quantity result and select top 20 percent quantity from table name query result It’s the same, don’t understand, hope to explain

wgfxman

Without SUM(), the detailed data will come out
With SUM(), the result is the summary data (sum)

wgfxman

Another point is that it uses variables to store the results. If you don't use SUM() and return multiple records, select @departtotal = sum(number) will cause an error.

Using SUM(), the result is to ensure that there is only one summary data, and the above error will not occur.

haigerrual

wrong
Something happened just now
Sorry

haigerrual

Yep
Who knows why the first sentence
select top 20 percent @departtotal=sum(number) from table name
with
select sum (number) from table name
The result is the same