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How can you represent inheritance in a database?
...table as in your first option is probably the simplest design. As you mentioned, many attributes that are subtype-specific will have to be given a NULL value on rows where these attributes do not apply. With this model, you would have one policies table, which would look something like this:
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PostgreSQL - fetch the row which has the Max value for a column
... vary in production based on actual machine load/data access spread. When one query appears slightly faster (<20%) than the other but has a much higher cost, it will generally be wiser to choose the one with higher execution time but lower cost.
When you expect that there will be no competition...
Insert into … values ( SELECT … FROM … )
...ondition changed to table2.country and returns number of rows greater than one? I got similar issue here: stackoverflow.com/questions/36030370/…
– vijayrana
Mar 17 '16 at 6:25
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What is the difference between Cloud, Grid and Cluster? [closed]
... essentially smashing up many machines to make a really big & powerful one. This is a much more difficult architecture than cloud or grid to get right because you have to orchestrate all nodes to work together, and provide consistency of things such as cache, memory, and not to mention clocks. O...
Want to find records with no associated records in Rails
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This is still pretty close to SQL, but it should get everyone with no friends in the first case:
Person.where('id NOT IN (SELECT DISTINCT(person_id) FROM friends)')
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Why should I use a pointer rather than the object itself?
...g from a Java background and have started working with objects in C++. But one thing that occurred to me is that people often use pointers to objects rather than the objects themselves, for example this declaration:
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How do I create an empty array/matrix in NumPy?
...mally use a list. I want to create an empty array (or matrix) and then add one column (or row) to it at a time.
13 Answers
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Android: java.lang.SecurityException: Permission Denial: start Intent
... android:exported
Whether or not the activity can be launched by components of other applications — "true" if it can be, and "false" if not. If "false", the activity can be launched only by components of the same application or applications with the same user ID.
The default value depen...
How to add an extra column to a NumPy array
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@Outlier you should post a new question rather than ask one in the comments of this one.
– JoshAdel
Dec 10 '14 at 16:37
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Integer.toString(int i) vs String.valueOf(int i)
... of doing the same thing. It may be a historical reason (can't remember if one came before the other).
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