大约有 9,000 项符合查询结果（耗时：0.0211秒） [XML]
Why all the Active Record hate? [closed]
...
end
people = Person.find(:all, :include => :company )
This generates SQL with LEFT JOIN companies on companies.id = person.company_id, and automatically generates associated Company objects so you can do people.first.company and it doesn't need to hit the database because the data is already p...
Using IQueryable with Linq
...t;= 25.00);
The code looks the same, but the difference here is that the SQL executed will be SELECT * FROM Products WHERE Cost >= 25.
From your POV as a developer, this looks the same. However, from a performance standpoint, you may only return 2 records across the network instead of 20,000....
SQL JOIN - WHERE clause vs. ON clause
After reading it, this is not a duplicate of Explicit vs Implicit SQL Joins .
The answer may be related (or even the same) but the question is different.
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Change Oracle port from port 8080
...nvironmental variables are set correctly start with the following:
C:\>sqlplus /nolog
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Aug 26 10:40:44 2008
Copyright (c) 1982, 2005, Oracle. All rights reserved.
SQL> connect
Enter user-name: system
Enter password: <enter password if will ...
The specified type member 'Date' is not supported in LINQ to Entities Exception
...not translate most .NET Date methods (including the casting you used) into SQL since there is no equivalent SQL.
The solution is to use the Date methods outside the LINQ statement and then pass in a value. It looks as if Convert.ToDateTime(rule.data).Date is causing the error.
Calling Date on a Da...
SQL Add foreign key to existing column
If I am using the following SQL command in SQL Server 2008 to update a table with a foreign key constraint:
6 Answers
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Best way to work with transactions in MS SQL Server Management Studio
Let's say I have an SQL statement that's syntactically and semantically correct so it executes.
2 Answers
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Difference between JOIN and INNER JOIN
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Is this true for all data bases (e.g. SQL, postgres?) Does anyone know a link to the documentation explaining this?
– Chogg
Oct 25 '17 at 17:32
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What exactly is Arel in Rails 3.0?
...ement for ActiveRecord
No, it isn't. It's a replacement for hand-crafting SQL queries in strings. It is a common query layer that underlies ActiveRecord, but it can also be used as an underpinning for DataMapper, for example.
If it is a replacement for anything, it's a replacement for Ambition. Or,...
1052: Column 'id' in field list is ambiguous
...
SQL supports qualifying a column by prefixing the reference with either the full table name:
SELECT tbl_names.id, tbl_section.id, name, section
FROM tbl_names
JOIN tbl_section ON tbl_section.id = tbl_names.id
...or a ta...