How do I suppress or ignore errors in a SQL SELECT statement

Question

Anyone know how to suppress / ignore errors in a select statement?

My select statement uses the STLineFromText function, and when it hits an invalid line, it raises an error. I'm ok with ignoring the bad rows, and cannot really change my source data.

Here is a sample query that demonstrates my problem:

SELECT geography::STLineFromText('LINESTRING(-74.2204037952351 40.4283173372472,-74.2204851952350 40.4283519372471)', 4326) UNION ALL
SELECT geography::STLineFromText('LINESTRING(-74.2316367952177 40.4386102038979,-74.2313671952181 40.4388540705641)', 4326) UNION ALL
SELECT geography::STLineFromText('LINESTRING(-74.2229282618978 40.4252709372519,-74.2229171285645 40.4252638039186,-74.2229282618978 40.4252709372519,-74.2227441952315 40.4251499372521,-74.2231121285642 40.4243291372534)', 4326) UNION ALL
SELECT geography::STLineFromText('LINESTRING(-74.2418989952017 40.4417621372263,-74.2417773285352 40.4417915372263)', 4326) UNION ALL
SELECT geography::STLineFromText('LINESTRING(-74.2166069952410 40.4334496039059,-74.2158269952422 40.4336396039056)', 4326)

and here is the error:

Msg 6522, Level 16, State 1, Line 2
A .NET Framework error occurred during execution of user-defined routine or aggregate "geography": 
System.ArgumentException: 24200: The specified input does not represent a valid geography instance.
System.ArgumentException: 
   at Microsoft.SqlServer.Types.SqlGeography.ConstructGeographyFromUserInput(GeoData g, Int32 srid)
   at Microsoft.SqlServer.Types.SqlGeography.GeographyFromText(OpenGisType type, SqlChars taggedText, Int32 srid)

The ideal situation would be to just return #1, #2, #4 & #5, ignoring #3

Thanks!

Answer 1

So I bit the bullet and wrote my own CLR function so that I could incorporate a try/catch. It's working pretty well.

<Microsoft.SqlServer.Server.SqlFunction()> _
Public Shared Function STLineFromTextFlexible(ByVal LineString As SqlChars, ByVal SRID As Integer) As Microsoft.SqlServer.Types.SqlGeography
    Try
        Dim Geo As New SqlGeography()

        Geo = SqlGeography.STLineFromText(LineString, SRID)

        Return Geo
    Catch ex As Exception
        Return Nothing
    End Try
End Function

Credits:

http://msdn.microsoft.com/en-us/library/w2kae45k(v=vs.80).aspx

http://msdn.microsoft.com/en-us/library/ms131065.aspx

Answer 2

No; to answer your original question, you can't simply have SQL Server "ignore" the errors. The only way to do this server-side would be to create a UDF that takes the same parameters as STLineFromText but encloses the call in a try / catch block and returns null in the case of an exception.

OK, scratch that, since you can't try / catch in a function. What you could do, however, is define a UDF that's a pass-thru to an OPENQUERY call to a stored procedure that takes the value as a parameter. Then you can go have a stiff drink.

Something along the lines of...

CREATE PROCEDURE SP_IgnoreErrors(@value varchar(255), @param int)
AS
BEGIN
    BEGIN TRY
        SELECT geography::STLineFromText(@value, @param) AS VALUE
    END TRY
    BEGIN CATCH
        SELECT NULL AS VALUE
    END CATCH
END

CREATE FUNCTION IgnoreErrors(@value varchar(255), @param int) RETURNS XXX
AS
BEGIN
    DECLARE @output XXX

    SELECT @output = VALUE from OPENQUERY([YOURINSTANCE],'Database.dbo.SP_IgnoreErrors ''' + @value + ''', ' + convert(varchar, @param))

    RETURN @output
END

This is, of course, an abomination. I don't have SSMS in front of me, but even if this doesn't compile it should at least be enough to go on to tweak it into something that does.