ISNUMERIC returns a confusing result

• john.masheter

  SSC Rookie

  Points: 45

  More actions

  July 25, 2008 at 5:13 am

  #188368

  We recently stumbled across a problem in our data where we'd uploaded a file with a comma instead of a decimal point in a number into a varchar field. Yes, I know it should have been in a decimal field if we're going to deal with it as a number and yes, I know it should be validated but that's not the point of the question.

  My question is more about understanding SQL Server.

  Why does this:

  SELECT ISNUMERIC ('5,0')

  return true, yet this:

  SELECT CAST('5,0' AS DECIMAL(20,10))

  fails because it's not a number?

• ChrisM@Work

  SSC Guru

  Points: 186127

  More actions

  July 25, 2008 at 5:27 am

  #848307

  Hi John

  The shortfalls of ISNUMERIC have been discussed many times before. This should help:

  http://www.sqlservercentral.com/Forums/Topic456023-338-1.aspx

  Cheers

  ChrisM

  ^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

  For fast, accurate and documented assistance in answering your questions, please read this article.
  Understanding and using APPLY, (I) and (II) Paul White
  Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

• john.masheter

  SSC Rookie

  Points: 45

  More actions

  July 25, 2008 at 5:36 am

  #848314

  thanks chris, that makes sense now i think about it. next time that catches me out i'll know why !!

  cheers

  John

• ChrisM@Work

  SSC Guru

  Points: 186127

  More actions

  July 25, 2008 at 5:42 am

  #848318

  You're welcome John, thanks for the feedback.

  There's a searchbox in the top right corner of the forum pages, if you enter ISNUMERIC Moden, you will get a whole bunch of useful discussion and lots of testing to support the conclusions.

  Cheers

  ChrisM

  ^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

  For fast, accurate and documented assistance in answering your questions, please read this article.
  Understanding and using APPLY, (I) and (II) Paul White
  Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden