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| visits | member for | 1 year, 2 months |
| seen | 23 hours ago | |
| stats | profile views | 50 |
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Apr 3 |
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Handling expiration in a course registration or ticketing system And in addition, create views such as REGISTRATION_EXPIRED_WITHOUT_PAYMENT and REGISTRATION_UNPAID_UNEXPIRED. |
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Mar 13 |
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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. |
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Mar 12 |
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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 ? |
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Mar 2 |
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Why is optimistic locking faster than pessimistic locking? No it doesn't. That's why it's "faster". |
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Feb 20 |
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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. |
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Feb 18 |
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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 ... |
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Feb 18 |
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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. |
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Feb 1 |
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What is the correct result for this query? @Kevin did you ask ISO for permission to copy ? :-) |
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Jan 29 |
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What is the correct result for this query? Well the key issue is whether it's indeed true that "even if the table has no rows at all, it's still one group of 0 rows". And the standard turns out to be explicit about this : "If there are no grouping columns, then ... is the grouped table consisting of T as its only group". (and that holds even if T is empty - so there is indeed a group.) Further on, the having clause specifies that the condition is applied to each group (in the example thus once). They probably defined it this way to make SUM and COUNT return one row even for empty T's. |
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Jan 24 |
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How to tackle a large undocumented database Think before you comment. The OP explicitly stated that he was the ONLY It guy. So who are those developers ? External contractors perhaps, who were paid for nothing more than just the time it took to build the thing ? Why would those be willing to put in their time for additional support, which company X probably has been unwilling to pay for to begin with ? Or were they perhaps former employees who got laid off because they were too expensive ? Why would they put in their time to help out company X with its problems ? And who is going to get hurt by dropping tables ? |
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Dec 14 |
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Simplify and optimize a complex query Then you'll have to make the users accept the 35 seconds (and its further degrading as data volumes grow faster than the hardware speeds do). Forewarning them about this (as in : display a rotating clockwork to make it clear that the machine is working at their service) sometimes works miracles in this respect. |
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Dec 11 |
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Searching transaction logs for changes you'll have to specify which SQL product you're using. |
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Dec 3 |
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How to best encapsulate monetary values in a database Option 1 is not anti-relational and it is not true that there isn't a "purely relational solution to this". Except then perhaps for extremely perverse interpretations of "purely relational". |
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Nov 2 |
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“Zero” downtime and minimal space requirements for upgrade to PostgreSQL 9.2 Providing only version numbers without naming the product isn't exactly helpful ... |
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Oct 11 |
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Is there a reason to use extremely abbreviated table names? If 30 characters aren't enough to be able to come up with unique names for tables, you have a much more serious problem than any DBMS or development environment can solve : you have a problem with the level of expressiveness of your language and/or vocabulary. |
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Oct 5 |
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Why does ANSI SQL define SUM(no rows) as NULL? I've typed some stuff in that second link you gave ... |
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Oct 5 |
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Why does ANSI SQL define SUM(no rows) as NULL? The space available in these comments is way too short to discuss all that in the level of detail it deserves. Is there some place else where we can take these discussions to ? |
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Oct 5 |
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Why does ANSI SQL define SUM(no rows) as NULL? @AlexKuznetsov : sorry to say, but what about SUM ( { 1 3 } ) + SUM ( { 1 4 } ) == SUM ( { 1 3 } UNION { 1 4 } ) ? Remember that relational union is supposed to eliminate duplicates !!! |
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Oct 5 |
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Why does ANSI SQL define SUM(no rows) as NULL? @SQL kiwi. Are you forgetting about static type checking ? If expressions like SUM() are handled by the static type checker as if they always return an integer, then obviously it should be impossible for the SUM() invocation to sometimes return something that is not an integer (e.g. an empty relation). |
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Oct 5 |
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Why does ANSI SQL define SUM(no rows) as NULL? @TToni : "especially when you think about possible expansions of the standard" is not the context that the OP was referring to. the OP was very clearly referring to the current version of the standard, which does not include any sort of notion of "dynamic types" or some such. (Oh, and I only commented, but didn't downvote. Apart from that tiny slip I took issue with, nothing in your answer was wrong enough to warrant a downvote. IMO.) |
