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Difference between filter and filter_by in SQLAlchemy
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These code examples are misleading: Declarative base table classes and instances have neither filter nor query methods; they use the session.
– Turtles Are Cute
Mar 16 '16 at 19:45
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Virtual member call in a constructor
...y are constructed, but start out as the most derived type, with the method table being for the most derived type. This means that virtual method calls always run on the most derived type.
When you combine these two facts you are left with the problem that if you make a virtual method call in a cons...
MySQL 启动报错 Table \'mysql.plugin\' doesn\'t exist - 数据库(内核) -...
MySQL 启动报错 Table 'mysql.plugin' doesn't exist 启动报错： opt szy bin mysqld: Table 'mysql.plugin ' doesn 't exist141211 15:06:12 [ERROR] Can 't open t...启动报错：
/opt/szy/bin/mysqld: Table \'mysql.plugin\' doesn\'t exist
141211 15:06:12 [ERROR] Can\'t open the mysql.plug...
How to include “zero” / “0” results in COUNT aggregate?
...u want an outer join for this (and you need to use person as the "driving" table)
SELECT person.person_id, COUNT(appointment.person_id) AS "number_of_appointments"
FROM person
LEFT JOIN appointment ON person.person_id = appointment.person_id
GROUP BY person.person_id;
The reason why this is wo...
A std::map that keep track of the order of insertion?
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You might combine a std::vector with a std::tr1::unordered_map (a hash table). Here's a link to Boost's documentation for unordered_map. You can use the vector to keep track of the insertion order and the hash table to do the frequent lookups. If you're doing hundreds of thousands of lookups,...
How to check if a function exists on a SQL database
...s for this type argument, particularly:
FN : Scalar function
IF : Inline table-valued function
TF : Table-valued-function
FS : Assembly (CLR) scalar-function
FT : Assembly (CLR) table-valued function
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How to express a NOT IN query with ActiveRecord/Rails?
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Using Arel:
topics=Topic.arel_table
Topic.where(topics[:forum_id].not_in(@forum_ids))
or, if preferred:
topics=Topic.arel_table
Topic.where(topics[:forum_id].in(@forum_ids).not)
and since rails 4 on:
topics=Topic.arel_table
Topic.where.not(topics[:f...
Is a DIV inside a TD a bad idea?
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Using a div instide a td is not worse than any other way of using tables for layout. (Some people never use tables for layout though, and I happen to be one of them.)
If you use a div in a td you will however get in a situation where it might be hard to predict how the elements will be siz...
PHP: How to generate a random, unique, alphanumeric string for use in a secret link?
...unctions, then we can generate highly reliable unique strings. Here is the table showing my research data:
Update:
I created a simple Heroku app using these functions that returns the token as a JSON response. The app can be accessed at https://uniquestrings.herokuapp.com/api/token?length=15
I hope...
Why are C# interface methods not declared abstract or virtual?
...phic with regards to the interface type, so it needs a slot on the virtual table to allow virtual method dispatching.
– Jordão
Sep 1 '10 at 20:06
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