Rails SQL 查询构建器...或 ActiveRecord 查询构建器

Question

我需要像这样运行 sql 查询

sql = 'SELECT * FROM users WHERE id != ' + self.id.to_s + ' AND id NOT IN (SELECT artner_id FROM encounters WHERE user_id = ' + self.id.to_s + ')'
sql += ' AND id NOT IN (SELECT user_id FROM encounters WHERE partner_id = ' + self.id.to_s + ' AND predisposition = ' + Encounter::Negative.to_s + ')'
sql += ' AND cfg_sex = ' + self.sex.to_s + ' AND cfg_country = ' + self.country.to_s + ' AND cfg_city = ' + self.city.to_s
sql += ' ORDER BY rand() LIMIT 1'

可以通过AR.find_by_sql执行，但是之前的代码可读性差。是否有任何查询构建器可以构建该查询？

例如，Kohana（它是 PHP 框架，我是 php 开发人员，但我想将该语言更改为 ruby​​/rails）有一个查询构建器，其工作方式如下：

$sql = DB::select('*')->from('users');
$sql->where('id', 'NOT_IN', DB::expr('SELECT partner_id FROM encounters WHERE user_id = '.$user->id));
$sql->where('id', 'NOT_IN', DB::expr('SELECT user_id FROM encounters WHERE partner_id = '.$user->id.' AND predisposition = '.Encounter::Negative));
....
etc
...

使用类似 Kohana 查询构建器的查询构建器构建的查询更具可读性和可理解性。

有什么宝石可以解决这个问题吗？

Answer 1

你需要squeel gem。它使用块扩展AR，并轻松进行非常复杂的查询。

只是几个特点：

# not_in == cool! )
Product.where{id.not_in LineItem.select{product_id}}
# SELECT "products".* FROM "products" WHERE "products"."id" NOT IN 
# (SELECT "line_items"."product_id" FROM "line_items" )

# outer joins on pure Ruby:
LineItem.joins{product.outer}
# LineItem Load (0.0ms)  SELECT "line_items".* FROM "line_items" 
# LEFT OUTER JOIN "products" ON "products"."id" = "line_items"."product_id"

# calcs, aliasing:
Product.select{[avg(price).as(middle)]}
# SELECT avg("products"."price") AS middle FROM "products"

# comparison
Product.where{id != 100500}
Product.where{price<10}

# logical OR
Product.where{(price<10) | (title.like '%rails%')}
# SELECT "products".* FROM "products" WHERE (("products"."price" < 10 OR
# "products"."title" LIKE '%rails%'))

# xxx_any feature (also available xxx_all)
Product.where{title.like_any %w[%ruby% %rails%]}
# SELECT "products".* FROM "products" WHERE (("products"."title" LIKE '%ruby%' OR 
# "products"."title" LIKE '%rails%'))    

注意 using 块：{...}这里不是哈希。还要注意没有符号。

如果您决定选择它，请阅读以“这带有重要含义”开头的部分