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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
The "N+1 selects problem" is generally stated as a problem in Object-Relational mapping (ORM) discussions, and I understand that it has something to do with having to make a lot of database queries for something that seems simple in the object world.
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Get value when selected ng-option changes
...ple:
<div ng-app="App" >
<div ng-controller="ctrl">
<select ng-model="blisterPackTemplateSelected" ng-change="changedValue(blisterPackTemplateSelected)"
data-ng-options="blisterPackTemplate as blisterPackTemplate.name for blisterPackTemplate in blisterPackTemplates...
How to reset postgres' primary key sequence when it falls out of sync?
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-- Login to psql and run the following
-- What is the result?
SELECT MAX(id) FROM your_table;
-- Then run...
-- This should be higher than the last result.
SELECT nextval('your_table_id_seq');
-- If it's not higher... run this set the sequence last to your highest id.
-- (wise to run...
How to randomly select rows in SQL?
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SELECT TOP 5 Id, Name FROM customerNames
ORDER BY NEWID()
That said, everybody seems to come to this page for the more general answer to your question:
Selecting a random row in SQL
Select a random row with MySQL:
SELECT...
Select random row from a sqlite table
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Have a look at Selecting a Random Row from an SQLite Table
SELECT * FROM table ORDER BY RANDOM() LIMIT 1;
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Select first row in each GROUP BY group?
As the title suggests, I'd like to select the first row of each set of rows grouped with a GROUP BY .
17 Answers
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How to get multiple counts with one SQL query?
...tion. This is basically the same thing as a PIVOT function in some RDBMS:
SELECT distributor_id,
count(*) AS total,
sum(case when level = 'exec' then 1 else 0 end) AS ExecCount,
sum(case when level = 'personal' then 1 else 0 end) AS PersonalCount
FROM yourtable
GROUP BY distributor_id
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Why isn't vector a STL container?
...l directly. Workarounds to
avoid this range from using a different type (char, unsigned char) or
container (like deque) to use wrapper types or further specialize for
specific allocator types.
bitset is a class that provides a similar functionality for fixed-size
arrays of bits.
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What XML parser should I use in C++? [closed]
...what library you should use depends on your needs. Here's a convenient flowchart:
So the first question is this: What do you need?
I Need Full XML Compliance
OK, so you need to process XML. Not toy XML, real XML. You need to be able to read and write all of the XML specification, not just the low-l...
how to use ng-option to set default value of select element
I've seen the documentation of the Angular select directive here: http://docs.angularjs.org/api/ng.directive:select .
I can't figure how to set the default value. This is confusing:
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