Spaces in Oracle fields

Hi,

I have an Oracle table which contains a number of CHAR fields. Some of these fields are truely NULL, others appear to be NULL on screen forms but actually contain 1 or more spaces, entered by careless users. Reports and programs which check for NULL values in various fields are therefore not always selecting the expected records. In the short term I need an SQL update statement to set a field to NULL if it contains spaces (and only spaces). In the longer term I need to prevent users from filling a screen field with spaces only.

Any ideas ?

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Tony Desborough                                                 SRL Data Ltd
Software Programmer                                             1, Perren St
Email: tony_at_bilpin.co.uk                                     LONDON, NW5 3ED