Divide by zero error encountered and division

Question

Divide by zero error encountered and division

nymets86

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Points: 191
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April 14, 2020 at 6:27 pm

#3742836

Having trouble with the below statement. Please help if you can. I am not that great with SQL but trying to get better. Thanks in advance. Getting the divide by zero error because of 0s in the numerator.
select CAST(ROUND(COLUMN_A *100.0 / COLUMN_B,2) as decimal(5,2)) as "Percentage" from TABLE

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Mr. Brian Gale SSC-Insane Points: 24800 More actions · Answer 1

My expectation is that COLUMN_B has 0 values. So you need to exclude those or do something with them such as setting them to 1. how you handle it depends on your data and what you are trying to do. For example, you could put a where clause on and filter out everything where COLUMN_B is 0 or you could change COLUMN_B to NULL when it is 0, or could use a CASE statement to change it to another value when it is 0.

for suggestion 1:

select CAST(ROUND(COLUMN_A*100/COLUMN_B,2) as decimal(5,2)) as "Percentage" from TABLE WHERE COLUMN_B <> 0

for suggestion 2:

select CAST(ROUND(COLUMN_A*100.0/NULLIF(COLUMN_B,0),2) as decimal(5,2)) as "Percentage" from TABLE

for suggestion 3:

select CAST(ROUNT(COLUMN_A*100.0/(CASE WHEN COLUMN_B = 0 then -1 ELSE COLUMN_B END) as decimal(5,2)) as "Percentage" from TABLE

There may be other solutions too... it really depends on what you want to do when the value is 0.

The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.

nymets86 SSC Enthusiast Points: 191 More actions · Answer 2

thanks so much for the fast reply. I will try all of your solutions then post which one worked for me. much appreciated.

nymets86 SSC Enthusiast Points: 191 More actions · Answer 3

select CAST(ROUND(COLUMN_A*100.0/(CASE WHEN COLUMN_B = 0 then -1 ELSE COLUMN_B END) as decimal(5,2)) as "Percentage" from TABLE

I think this is the one I need but I am getting a syntax error.

Incorrect syntax near the keyword 'AS'.

Do you know what is wrong with this?

I basically want to do the divide calculation and if there is a zero apply a % of 0 to the row.

Mr. Brian Gale SSC-Insane Points: 24800 More actions · Answer 4

So, if I understand correctly, if it is going to divide by 0, then you want it to return 0 instead. Then none of the solutions I provided will help actually. In that case, you likely want something like:

SELECT CAST(ROUND(COLUMN_A*100/COLUMN_B,2) as decimal(5,2)) AS "Percentage" 
FROM TABLE 
WHERE COLUMN_B <> 0
UNION ALL
SELECT 0
FROM TABLE
WHERE COLUMN_B = 0

OR

SELECT CASE COLUMN_B 
    WHEN 0 THEN 0
    ELSE CAST(ROUND(COLUMN_A*100/COLUMN_B,2) as decimal(5,2)) 
    END AS "Percentage" 
FROM TABLE

Both should give you the same result, just ordered differently. Different execution plans and thus different performance.

First one does the calculation when the value of COLUMN_B is non-zero and does a UNION to get 0 when it is zero. The second one does that all in a single select...

The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.

Jeffrey Williams SSC Guru Points: 90303 More actions · Answer 5

Maybe this will give you some ideas:

Declare @testTable Table (column_a int, column_b int);

 Insert Into @testTable (column_a, column_b)
 Values (10,  3)
      , ( 1,  2)
      , (10,  0)
      , ( 1,  5);

 Select *
      , cast(tt.column_a * 100.0 / coalesce(nullif(tt.column_b, 0), tt.column_a) As decimal(5,2))
   From @testTable tt;

Jeffrey Williams
“We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”

― Charles R. Swindoll

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ratbak Ten Centuries Points: 1359 More actions · Answer 6

SELECT CAST(ROUND(COLUMN_A*100.0/(CASE WHEN COLUMN_B = 0 THEN -1 ELSE COLUMN_B END),2) as decimal(5,2)) as "Percentage"

You lost the ROUND() function's length parameter in that version

Mr. Brian Gale SSC-Insane Points: 24800 More actions · Answer 7

ratbak wrote:

SELECT CAST(ROUND(COLUMN_A*100.0/(CASE WHEN COLUMN_B = 0 THEN -1 ELSE COLUMN_B END),2) as decimal(5,2)) as "Percentage"
You lost the ROUND() function's length parameter in that version

Good catch. That's what I get for posting code without testing it :P. Should have the ",2)" before "as decimal" as you corrected.

The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.

nymets86 SSC Enthusiast Points: 191 More actions · Answer 8

thanks so much to both of you. the last formula worked for me and I appreciate you both taking the time to help me. cheers!