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Good MapReduce examples [closed]
... values and perform any sort of transformations on these.
For Example In SQL, Given the Date of Birth, to find out How many people are of age > 30 for a million records would take a while, and this would only increase in order of magnitute when the complexity of the query increases.
Map Reduce...
Rails: Default sort order for a rails model?
...efault_scope { order(created_at: :desc) } if, like me, you try to minimize sql syntax in rails.<br/>If you have multiple columns to order by and you want to use the new syntax you may need to wrap the desc columns in mustaches like this default_scope { order({begin_date: :desc}, :name) }
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Is there a software-engineering methodology for functional programming? [closed]
...elational definition of the essential state in clojure without reinventing sql (without its flaws)? Or is the idea to simply use a good relational (sql) DB and built a functional program on top of it without the conceptual mismatch introduced by OOP?
– Thorsten
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What's the false operator in C# good for?
...ample >0 for true, <0 for false and ==0 for null, and then you'd get SQL-style null semantics. You would also have to implement a .IsNull method or property in order that nullity could be checked explicitly.
Comparing to SQL, imagine a table Table with 3 rows with value Foo set to true, 3 ro...
What is Normalisation (or Normalization)?
...y a number. A higher number means fewer redundancies and dependencies. Any SQL table is in 1NF (first normal form, pretty much by definition) Normalizing means changing the schema (often partitioning the tables) in a reversible way, giving a model which is functionally identical, except with less re...
Best way to select random rows PostgreSQL
I want a random selection of rows in PostgreSQL, I tried this:
12 Answers
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Is there a REAL performance difference between INT and VARCHAR primary keys?
...performance difference between using INT vs. VARCHAR as a primary key in MySQL? I'd like to use VARCHAR as the primary key for reference lists (think US States, Country Codes) and a coworker won't budge on the INT AUTO_INCREMENT as a primary key for all tables.
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How to choose the id generation strategy when using JPA and Hibernate
...ble. Do not use in a cluster.
identity
supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int.
sequence
uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a generator in Interbase. The returned identifier is o...
Reference - What does this error mean in PHP?
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Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given
First and foremost:
Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn...
ExecuteReader requires an open and available Connection. The connection's current state is Connectin
When attempting to connect to MSSQL database via ASP.NET online, I will get the following when two or more people connect simultaneously:
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