At 06:18 PM 12/7/2013, Dr. Fritz Luettgens wrote:
In my table not all colums have values, but duplicates exist.
My standard setting is: SET EQNULL OFF, NULL: -0-
I want: DELETE DUPLICATES FROM TABLE
result is: 0 duplicates have been deleted
but when: SET EQNULL ON
the command is successful: n duplicates have been deleted !
Question: Should this command not also work on a table with setting
SET EQNULL OFF ?
Dr. Fritz,
Here's a technical explanation ...
When using the DELETE DUPLICATES command without specifying the
"USING columnname",
all matching rows and columns, including the columns with NULL values
are evaluated.
The EQNULL setting as TRUE (ON) means that a comparison between two
NULL values is
a match and that a comparison between a NULL value and a non-NULL
value is not.
When EQNULL is set to FALSE (OFF) then a comparison between two NULL
values is not
a match nor is a comparison between a NULL value and a non-NULL value
a mismatch.
The NULL value essentially make the whole thing "unknown'.
Hope that helps you understand the difference.
If you need a few examples to understand this whole thing
practically, feel free
to reach out to me with further questions.
Very Best R:egards,
Razzak.
www.rbase.com
www.facebook.com/rbase
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