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Eager load polymorphic
...able alone, since multiple tables represent the other end of the join, and SQL, as far as I know, does not allow you join a table named by the value stored in a column. By defining the extra relationship belongs_to :shop, you are giving ActiveRecord the information it needs to complete the join.
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Use email address as primary key?
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@onedaywhen: Yep! Otherwise why would SQL support cascading updates?
– Bill Karwin
Sep 27 '10 at 17:52
18
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How to sort objects by multiple keys in Python?
...der.
This means that the equivalent of ORDER BY name ASC, age DESC (using SQL notation) for a list of dictionaries can be done like this:
items.sort(key=operator.itemgetter('age'), reverse=True)
items.sort(key=operator.itemgetter('name'))
Note how the items are first sorted by the "lesser" attri...
How to implement a many-to-many relationship in PostgreSQL?
...itle is self-explanatory. How do you create the table structure in PostgreSQL to make a many-to-many relationship.
1 Answe...
What's the best way to join on the same table twice?
...o corresponding exists on the right. For me this works in Microsoft Access SQL (they require the parenthesis!)
SELECT t.PhoneNumber1, t.PhoneNumber2, t.PhoneNumber3
t1.SomeOtherFieldForPhone1, t2.someOtherFieldForPhone2, t3.someOtherFieldForPhone3
FROM
(
(
Table1 AS t LEFT JOIN Table2 AS t3 ...
控件重绘函数/消息OnPaint,OnDraw,OnDrawItem,DrawItem的区别 - C/C++ - 清...
...DrawItem()-àDrawItem();
4.DrawItem:虚函数,需要重载
如果使用DrawItem来自画控件,需要给控件加上自画样式,然后重载该控件类的自画函数(DrawItem)函数,如果该控件的父窗口提供了ON_WM_DRAWITEM消息映射宏,并重载了OnDrawItem函数,则重画...
“open/close” SqlConnection or keep open?
...ple static classes with static methods. Each of these methods opens/closes SQL connection when called:
6 Answers
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Give all the permissions to a user on a DB
...a DATABASE vs SCHEMA?
Grant privileges for a particular database in PostgreSQL
How to grant all privileges on views to arbitrary user
Consider upgrading to a current version.
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MySQL JOIN the most recent row only?
...virtually instantaneous (WorkBench literally says 0.000 seconds, even with sql_no_cache set), whereas doing the search in the join took multiple seconds to complete. Still baffled, but I mean you can't argue with results like that.
– Brian Leishman
Mar 21 '17 a...
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