Which sum sholud the C#-code at the top write out?

Question

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the following code is written in a aspx- site.

...
...
long sum = 0;
for ( int i = 0; i < 888; i++)
{
// GetIntFromSQL returns an int from an SQL-statement-resultset with one
// row, one column
sum += GetIntFromSQL("EXEC dbo.ObscureProcedure @i = "+ i.ToString());
};
Response.Write(sum.ToString());
...
...

Proceduren i Microsoft SQL Server ser ut enligt:
CREATE PROCEDURE dbo.ObscureProcedure
@i int
AS
BEGIN
SELECT
CASE
WHEN @i < 260 THEN
COUNT(*) * @i
ELSE
COUNT(*) * 260
END AS ObscureCount
FROM
VacationGadget
WHERE
@i < 714
END

if you drive it in i Microsoft SQL Server Management Studio the following procedure ...

EXEC dbo.ObscureProcedure @i = 528

... the you get :
ObscureCount
------------
3138460

(1 row(s) affected)

which sum sholud the C#-code at the top write out?

i need help solving this? i don't know how to count it ? I'm new at this, please help

What I have tried:

i have tried to find info about how i should calculate this problem but without luck. i want to understand the formula to solve this. what should i multiple with what and add and so on.

Posted 26-Sep-17 3:51am

Member 13430887

Updated 26-Sep-17 8:42am

OriginalGriff

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Comments

Richard MacCutchan 26-Sep-17 10:57am

Ask the person who wrote the code.

Richard Deeming 26-Sep-17 14:14pm

NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

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OriginalGriff · Answer 1 · 2017-09-26T04:09:00

Solution 1

Run it, and find out: it's going to depend on your data, which we do not have any access to.

Posted 26-Sep-17 4:09am

OriginalGriff

Richard Deeming · Answer 2 · 2017-09-26T08:42:00

Time for some mathematical magic! :)

Breaking the stored procedure down:

If @i is greater than or equal to 714, it returns nothing;
If @i is greater than or equal to 260, it returns 260 × C, where C is the number of records in the VacationGadget table;
If @i is less than 260, it returns @i × C;

With your sample run, @i is 528, and the result is 3,138,460. Therefore, since @i is greater than 260, we can deduce that C = 3,138,460 ÷ 260 = 12,071.

Now to the loop.

We can discount the first iteration, since 0 × anything = 0.
We can probably discount anything from 714 to 888 - assuming your GetIntFromSQL method does the right thing when the stored procedure doesn't return any results.
For 1 to 259, the result from SQL will be i × C.
Therefore, the total sum for that part of the loop will be:
(the sum of integers from 1 to 259) × C.
For 260 to 713, the result from SQL will be 260 × C.
Therefore, the total sum for that part of the loop will be (714 - 260) × 260 × C;

Plumbing some numbers in:

(the sum of integers from 1 to 259)
= 259 × 260 ÷ 2 (Why?[^])
= 33,670;
(714 - 260) × 260
= 454 × 260
= 118,040;

The final result will be:
33,670 × C + 118,040 × C
= 151,710 × C
= 151,710 × 12,071
= 1,831,291,410