Home/ Questions/Q 137593
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-11T07:07:50+00:00

I was looking at postgres question and it called for updating a table with

  • 0

I was looking at postgres question and it called for updating a table with random values.

I only noticed it was targeted at postgres after answering it, but in answering it I hit a mystery.

Here is my sample code in question:

create table #Buildings([Use] varchar(50), n int)  insert #Buildings select null,null from sysobjects   update #Buildings set [Use] =          case (ABS(CAST(CAST(NEWID() AS VARBINARY) AS int)) % 6)             when 0 then null             when 1 then 'warehouse'             when 2 then 'office'             when 3 then 'market'             when 4 then 'retail'             when 5 then 'workshop'             else 'HOW IS THIS POSSIBLE'         end,     n = ABS(CAST(CAST(NEWID() AS VARBINARY) AS int)) % 6  select [Use], count(*) from #Buildings group by [Use]   select n, count(*) from #Buildings group by n

It returns a very odd result set: 

Use                                                 -------------------------------------------------- ----------- workshop                                           128 HOW IS THIS POSSIBLE                               633 NULL                                               287 retail                                             140 warehouse                                          258 market                                             177 office                                             209

And a second result set that makes complete sense:

n            ----------- ----------- 0           292 3           300 1           313 4           277 5           311 2           339

The data for both result sets was generated in the same update statement.

So my question is why is a number out of the range of 0 – 5 hitting my case statement? What is that number? Why when I update the int directly is stuff distributed properly?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. I have an idea:

    maybe the value is being computed on every when statement, if it gets to the first one, computes a value other than 0 it goes to the second, it then computes a value other than 1, then the next and so on, if it makes it’s way to 5 and then computes a number other than 5 it goes to else.

    this would also explain why there are so many more ‘HOW IS THIS POSSIBLE’ than the others, the others are incremented when the current position and the random number generated at that position match.

    your thoughts?

    edit: also i’ve tested in sql server express 2008 and it’s the same outcome.

    • 0