Active Record Query Interface 数据查询接口(界面)

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http://guides.rubyonrails.org/active_record_querying.html

 

This guide covers different ways to retrieve data from the database using Active Record.

After reading this guide, you will know:

?How to find records using a variety of methods and conditions.

?How to specify the order, retrieved attributes,grouping, and other properties of the found records.

? How to use eager loading(预先积极加载) to reduce the number of database queries needed for data retrieval.

? How to use dynamic finder methods.

? How to use method chaining to use multiple Active Record methods together. 

? How to check for the existence of particular records

? How to perform to do sth useful or difficult various calculations on Active Record models.

? How to run EXPLAIN on relations.(如何在关联上跑explain命令) 

 


 

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