Why won't this SQL CAST work?

sql-server, sql-server-2000, t-sql

Solution

This test script works fine for me... I can only suggest that maybe your TaskId isn't an NVARCHAR(50) like you say? Try an sp_columns just to check...

CREATE Table #TaskData (TaskId NVARCHAR(50))
INSERT INTO #TaskData (TaskId) SELECT CONVERT(NVARCHAR(50), NEWID())
UPDATE #TaskData SET TaskId = CONVERT(NVARCHAR(50), NEWID())
DROP TABLE #TaskData

Problem

I have a `nvarchar(50)` column in a SQL Server 2000 table defined as follows: ``` TaskID nvarchar(50) NULL ``` I need to populate this column with random SQL GUID's using the `NEWID()` function (I am unable to change the column type to `uniqueidentifier`). I tried this: ``` UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar) ``` but I got the following error: Msg 8115, Level 16, State 2, Line 1 Arithmetic overflow error converting expression to data type nvarchar. I also tried: ``` UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar(50)) ``` but then got this error: Msg 8152, Level 16, State 6, Line 1 String or binary data would be truncated. I don't understand why this doesn't work but this does: ``` DECLARE @TaskID nvarchar(50) SET @TaskID = CAST(NEW() AS nvarchar(50)) ``` I also tried `CONVERT(nvarchar, NEWID())` and `CONVERT(nvarchar(50), NEWID())` but got the same errors. Update: Ok, my eyesight is going, the column size on the table is `nvarchar(32)` not 50. Deepest apologies for the timewasting and thanks for all the answers.

Original source