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postgresql - sql - count of `true` values
In the above table, if I do :
10 Answers
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Where do “pure virtual function call” crashes come from?
...will not happen if the base class has been declared with the __declspec(novtable) optimization (Microsoft specific). With that, it's entirely possible to call an overridden virtual method after the object has been deleted, which could mask the problem until it bites you in some other form. The _pure...
Finding the id of a parent div using Jquery
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This can be easily done by doing:
$(this).closest('table').attr('id');
You attach this to any object inside a table and it will return you the id of that table.
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Applying a function to every row of a table using dplyr?
...o create an appropriately vectorised function.
R provide pmax which is suitable here, however it also provides Vectorize as a wrapper for mapply to allow you to create a vectorised arbitrary version of an arbitrary function.
library(dplyr)
# use base R pmax (vectorized in C)
iris %>% mutate(max...
Difference between JOIN and INNER JOIN
...specify CROSS JOIN.
OR
For an inner join, the syntax is:
SELECT ...
FROM TableA
[INNER] JOIN TableB
(in other words, the "INNER" keyword is optional - results are the same
with or without it)
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Ruby on Rails: how do I sort with two columns using ActiveRecord?
...s, you should use the following more robust version: :order => ["DATE(#{table_name}.updated_at)", :price] (Note that :price is a symbol.)
– Jo Liss
Jul 31 '12 at 17:32
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What should every developer know about databases? [closed]
...r a nontrivial requirement is not a trivial task. You can't build good SQL tables if you misunderstand the relational model.
Physical data modeling is generally DBMS specific, and doesn't need to be learned in much detail, unless the developer is also the database builder or the DBA. What develope...
Why unsigned integer is not available in PostgreSQL?
...ter solution would be Postgres adding unsigned as a first class type. In a table with 20 million records, with and indexed field like this, you are wasting 40MB of space on unused bits. If you are abusing that across another 20 tables, you're now wasting 800MB of space.
– tpart...
What data type to use for hashed password field and what length?
...cker gains access to your database, they'd have to construct their rainbow table based on that salt. And that's just as much work as simply guessing the password.
– Bill Karwin
Sep 16 '10 at 7:14
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Saving results with headers in Sql Server Management Studio
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Try the Export Wizard. In this example I select a whole table, but you can just as easily specify a query:
(you can also specify a query here)
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