Tag Archives: sql

Rails 2.1: Aggregate Expressions

Posted on September 5, 2008 by Ashiq Alibhai

Rails 2.1 allows you to perform complex aggregate queries, such as Donation.sum(“amount * 3″). This makes complex calculations a snap! Rails provides functions for calculating the average, count, maximum, minimum, and the sum. Continue reading →

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Find_by_SQL

Posted on April 20, 2008 by Ashiq Alibhai

How can you use the find function if you have complex find criteria–such as searching by fields that don’t exist in the table for your class? Enter the find_by_sql function. It allows you to use arbitrary SQL to find the model records you want–everything from joins and where clauses to having clauses. Rails handles the nitty-gritty work of returning models that have the attributes you selected. Continue reading →

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Using SQL for complex SELECT/ORDER Criteria

Posted on November 5, 2007 by Ashiq Alibhai

How can you select model objects using a complex SQL criterion (such as ordering by a SUM of values)? The answer is to use the find_by_sql method. You can select complex fields, join tables, and sort on those fields–such as sum fields. Continue reading →

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