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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...lly, a lot of dbms have been quite poor when it comes to handling joins (MySQL being a particularly noteworthy example). So n+1 has, often, been notably faster than a join. And then there are ways to improve on n+1 but still without needing a join, which is what the original problem relates to.
How...
How do I enable MSDTC on SQL Server?
Is this even a valid question? I have a .NET Windows app that is using MSTDC and it is throwing an exception:
6 Answers
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Best way to check if object exists in Entity Framework?
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If you don't want to execute SQL directly, the best way is to use Any(). This is because Any() will return as soon as it finds a match. Another option is Count(), but this might need to check every row before returning.
Here's an example of how to use i...
How to generate a new Guid in stored procedure?
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With SQL Server you can use the function NEWID. You're using C# so I assume that you're using SQL Server. I'm sure other database system have similar functions.
select NEWID()
If you're using Oracle then you can use the SYS_GUI...
What are the respective advantages/limitations of Amazon RDS vs. EC2 with MySQL? [closed]
... you can consider EC2 + EBS RAID 0. Vanilla EC2 is a terrible option for MySQL hosting.
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Entity Framework: “Store update, insert, or delete statement affected an unexpected number of rows (
...ata (Which meant when you went to save it 0 rows actually got updated). In SQL terms, their update query's where clause contains the original value of every field in the row, and if 0 rows are affected it knows something's gone wrong.
The idea behind it is that you won't end up overwriting a change...
How can you hide database output in Rails console?
...trying use a pointer to a logger that is set to nil (source: Disable Rails SQL logging in console)
To turn it back on
ActiveRecord::Base.logger.level = 0
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MySQL Great Circle Distance (Haversine formula)
...ript that gets Longitude and Latitude values and then inputs them into a MySQL query. I'd like to make it solely MySQL. Here's my current PHP Code:
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SQLAlchemy: Creating vs. Reusing a Session
Just a quick question: SQLAlchemy talks about calling sessionmaker() once but calling the resulting Session() class each time you need to talk to your DB. For me that means the second I would do my first session.add(x) or something similar, I would first do
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Removing duplicate rows from table in Oracle
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You should do a small pl/sql block using a cursor for loop and delete the rows you don't want to keep. For instance:
declare
prev_var my_table.var1%TYPE;
begin
for t in (select var1 from my_table order by var 1) LOOP
-- if previous var equal cur...