We also have to define relation operators behavior: ==, =, <, >, <=, >=
when DATE and TIMESTAMP are used.
We have the following choices:
1. compare only date part ignoring the time with the exception for ==
operator which will make exact comparison. For this exact comparision
we also have two choices:
a. strict type checking => results always .F.
b. if dates are equal and time part in TIMESTAMP item is 0 then
result is .T. otherwise .F.
2. convert DATE to TIMESTAMP setting 00:00 as TIME and compare items
like two TIMESTAMP values.
In such way works xHarbour.
3. use asymmetric comparison like for strings so:
FIELD->DATETIME <= date()
will work but
date() => FIELD->DATETIME
won't.
Hi,
I vote 1b.
2 is also acceptable for me.
3 Well a can not even understand the third choice. The truth is, that
still do not understand string comparison in Clipper, but very well
understand strcmp() behaviour. I always use ==, and I change != to !( ==
), for strings. I had a luck, that using of <, > does not cause bugs in
my code, and I try to avoid using <=, >= for strings.
More on 1b vs 2. 1b gives more expected results for:
dDate := DATE()
DATETIME <= dDate
1b result is TRUE for yesterday and older timestamps, but it is also
true, for all timestamps of today, just as I expect writing
"DATETIME<=dDate".
2 results is TRUE for yesterday and older timestamps, and only a
midnight of today. If DATETIME is midnight + 1 milliseconds is not less
or equal to dDate. I guess writing "DATETIME<=dDate", you've did not
expected to include values of exactly midnight, and not include midnight
+ 1 millisecond.
Best regards,
Mindaugas
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