I have a table field with type of data varchar, without permission for
entrance of null data

Doubt:
If I don't type anything in the field, the validation of null values at
table level usually happens, however if I type some text and later to
exclude the text, the validation doesn't happen plus, in other words, it
accepts what it would be null value, or it will be that for the exclusion
the field is filled out with characters that are not treated in the
validation as being null.

Hi

I doubt that after editing it is null. The value is probably a zero length
string "".

You UI must then decide, if the length of a string is 0, it must write a
null instead of the zero length string.

Regards
--------------------------------
Mike Epprecht, Microsoft SQL Server MVP
Zurich, Switzerland

IM: m***@epprecht.net

MVP Program: http://www.microsoft.com/mvp

Blog: http://www.msmvps.com/epprecht/

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With what kind of program are you changing the values of the column, I think
you change them to '' (an empty string) which isn´t actually NULL. If you
change the Value of an attribute in EM you have to press CTRL + 0 to really
insert NULL. If you defined a check constaint at column level (ColumnName
datatype NOT NULL) this Constraint will fire. If you also don´t want to
allow empty string values you additionaly have to define a check constraint
which count the LENGTH of the string or checks for an empty string, I would
prefer that Constraint
(ColumnName datatype NOT NULL CHECK(LEN(ColumnName ) > 0)

HTH, Jens Suessmeyer.

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