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  • 0 posts edited
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  • 15 votes cast
Jan
3
comment Find the highest graded student, using Tuple Relational Calculus
"Tuple relational calculus does not have a set difference operator"
Oct
9
comment How to get performance benefits from a view vs subquery?
More importantly, if a CTE is referenced multiple times, this fact by itself is not sufficient to deduce that the optimal access paths for each of the contexts in which they appear are also identical. Think any CTE, with attributes say A and B, being tested once for "does it contain a tuple where A=1" and elsewhere being tested for "does it contain a tuple where B=7". The CTE is the same, the optimal access paths for the two usages of the CTE most likely aren't, and neither of them necessarily involves full evaluation.
Aug
16
answered Relations, dependencies and normal form
May
13
awarded  Caucus
Apr
20
awarded  Yearling
Apr
10
answered Column partially determining accepted values of another column, should be somehow normalized?
Apr
3
comment Handling expiration in a course registration or ticketing system
And in addition, create views such as REGISTRATION_EXPIRED_WITHOUT_PAYMENT and REGISTRATION_UNPAID_UNEXPIRED.
Apr
3
answered What happens to a Trigger if a table is dropped and rename and recreated with same name
Mar
28
awarded  Quorum
Mar
13
comment Representing SQL constraints on a table
Chris, The accepted answer in that post does not give a declarative solution, and the answer by AKuznetzov forces three extra columns upon the user, and I'm not sure it is entirely impossible for the user to have the integrity test fail because of mistakes in those extra three columns.
Mar
12
comment Representing SQL constraints on a table
Even if he dropped the floor condition, can he have his constraint enforced declaratively with those engines that you mention ?
Mar
12
answered Performing SELECT on EACH ROW in CTE or Nested QUERY?
Mar
2
answered Why is optimistic locking faster than pessimistic locking?
Mar
2
comment Why is optimistic locking faster than pessimistic locking?
No it doesn't. That's why it's "faster".
Feb
20
comment Database functional dependency BCNF help
As far as normal forms theory is concerned, yes. As far as logical database design is concerned, remember that xNF is not where the story ends.
Feb
19
answered Database functional dependency BCNF help
Feb
19
answered Multiple primary keys
Feb
18
comment ORDER BY clause is allowed over column that is not in SELECT list?
Or it wouldn't. A table is explicitly defined by the standard to be an "unordered collection of rows". Make that fit with ORDER BY clauses ...
Feb
18
comment ORDER BY clause is allowed over column that is not in SELECT list?
For the problem the OP describes, just putting the ORDER BY before the SELECT will do the job. Don't read too much into these kinds of "flowcharts of query processing". They are rarely intended for being 100% accurate and complete. Rather, they are intended for illustrating somewhat globally what goes on as a consequence of an SQL statement being issued.
Feb
14
answered Where can I find the SQL standard document?