September 13, 2016 at 10:31 pm
CELKO (9/13/2016)
(start_date, end_date) pairs the idiom has been that a null in the end_date means "eternity"in that context
My experience has been that it means one of two possible outcomes:
1) Eternity in that it is the biggest end date
2) Eternity in that , because there is no end date, the start date is null, and hence there is no time span
Using is not the same as eternity as the greatest in date. That is "9999–12–31" in the ISO standards. There may be local conventions based on who is doing this but that is it. And no on point number two, just because you know when some immortal begin to live, you do not know when he will die (ever get involved with the highlander series of movies?)
The SQL temporal model is incomplete, but we can fake it, we really need a plus or minus (eternity) just like the IEEE has its +inf and +inf symbols
Date of death is unknown for mortals as well.
Unless one is scheduled for an execution.
But even then - there are some options.
Anyway - the time of death is NULL for any living creature.
And it definitely is not eternity.
Simply - unknown, undefined.
Same may be said about the amount of money in a wallet you did not open.
It's unknown.
But definitely not anywhere near infinity.
1/0 = infinity.
It's a certain value, not NULL.
And NULL may be infinity. May be zero. Or anything in between.
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Code for TallyGenerator
September 14, 2016 at 6:48 am
(ever get involved with the highlander series of movies?)
Not after the first one, but I am a big fan of Lazarus Long.
__________________________________________________
Against stupidity the gods themselves contend in vain. -- Friedrich Schiller
Stop, children, what's that sound? Everybody look what's going down. -- Stephen Stills
September 14, 2016 at 9:09 am
At least the old adage has been proven - that any conversation left to run long enough on the internet will result in someone being likened to Hitler!
September 14, 2016 at 10:32 am
Yeah? Well how would *you* feel if Hitler said that about *you* ?!? :crazy:
__________________________________________________
Against stupidity the gods themselves contend in vain. -- Friedrich Schiller
Stop, children, what's that sound? Everybody look what's going down. -- Stephen Stills
September 14, 2016 at 2:39 pm
I almost forgot that when we added the OLAP functions, became pretty close to Dr. Codd's two kinds of null. We have a null. That is in the actual data, and the null, that is created by rollups, cubes, and grouping sets. Unfortunately I do not think that grouping () works with outer joins.
https://msdn.microsoft.com/en-us/.../ms178544.aspx
GROUPING is used to distinguish the null values that are returned by ROLLUP, CUBE or GROUPING SETS from standard null values. The NULL returned as the result of a ROLLUP, CUBE or GROUPING SETS operation is a special use of NULL. This acts as a column placeholder in the result set and means all.
Books in Celko Series for Morgan-Kaufmann Publishing
Analytics and OLAP in SQL
Data and Databases: Concepts in Practice
Data, Measurements and Standards in SQL
SQL for Smarties
SQL Programming Style
SQL Puzzles and Answers
Thinking in Sets
Trees and Hierarchies in SQL
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