How do I combine AND and OR using Sequel? - sql

Question

I want to generate a SQL query like the following using Ruby's Sequel:
SELECT * FROM Objects WHERE (color = "red" AND shape = "triangle") OR
(color = "blue" AND shape = "square") OR
(color = "green" AND shape = "circle")
I want to build this query programmatically from a list of conditions, so that I can do something like this:
conditions = [[[:color, "red"], [:shape, "triangle"]],
[[:color, "blue"], [:shape, "square"]],
[[:color, "green"], [:shape, "circle"]]]
DB[:Users].where(conditions.sql_or)
It doesn't have to follow that exact form, but I want to be able to build the conditions programmatically, so it's not sufficient to be able to construct this query by hand.

Answer 1

Try this:
conditions = [
{:color => "red", :shape => "triangle"},
{:color => "blue", :shape => "square"},
{:color => "green", :shape => "circle"}
]
head, *tail = *conditions
tail.inject(DB[:Users].filter(head)){|mem,obj| mem.or(obj) }
I get:
=> #<Sequel::Postgres::Dataset: "SELECT * FROM \"Users\" WHERE (((\"color\" = 'red') AND (\"shape\" = 'triangle')) OR ((\"color\" = 'blue') AND (\"shape\" = 'square')) OR ((\"color\" = 'green') AND (\"shape\" = 'circle')))">

Answer 2

I think this will return an equivalent result, using a different SQL query:
DB[:Objects].where('(color, shape) in ?', conditions.sql_value_list).sql
=> "SELECT * FROM `Objects` WHERE ((color, shape) in (('red', 'triangle'), ('blue', 'square'), ('green', 'circle')))"
sql_value_list is documented in http://sequel.rubyforge.org/rdoc/classes/Array.html
Otherwise use:
objects = DB[:Objects].where(conditions[0])
conditions[1 .. -1].each { |c| objects = objects.or(c) }
Which results in:
SELECT * FROM `Objects` WHERE (((`color` = 'red') AND (`shape` = 'triangle')) OR ((`color` = 'blue') AND (`shape` = 'square')) OR ((`color` = 'green') AND (`shape` = 'circle')))
I was looking at Iain's answer, and it's basically the same as my second one, only more succinct; I like its elegance.