在Rails 3应用程序中使用原始SQL查询？

我有一个临床模型,控制器有以下代码：

@clinical_income_by_year = Clinical.find_all_by_sql(SELECT date_format(c.transactiondate,'%Y') as Year,date_format(c.transactiondate,'%b') as Month,sum(c.LineBalance) as "Income"
                                                 FROM clinical c
                                                 WHERE c.Payments = 0 AND c.LineBalance <> 0
                                                 AND c.analysiscode <> 213
                                                 GROUP BY c.MonthYear;)

但是,当我运行该代码时,我得到一些与格式有关的错误.

Started GET "/clinicals" for 127.0.0.1 at 2012-04-29 18:00:45 +0100

SyntaxError (/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:6: syntax error,unexpected tIDENTIFIER,expecting ')'
...rmat(c.transactiondate,...                               ^
/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:7: syntax error,expecting keyword_end
...rmat(c.transactiondate,...                               ^
/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:8: syntax error,expecting keyword_end
...          sum(c.LineBalance) as "Income"
...                               ^
/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:10: syntax error,unexpected tCONSTANT,expecting keyword_end
...       WHERE c.Payments = 0 AND c.LineBalance <> 0
...                               ^
/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:10: syntax error,unexpected '>'
...yments = 0 AND c.LineBalance <> 0
...                               ^
/Users/dannymcclelland/Projects/premvet/app/controllers/clinicals_controller.rb:11: syntax error,unexpected '>'
...          AND c.analysiscode <> 213
...                               ^

在将sql查询导入控制器之前,我应该对sql查询做些什么吗？尽管查询可能有问题(它是在很久以前编写的),但它直接在数据库中运行时确实可以正常工作.它返回一个这样的数组：

----------------------------------------------
|  Year      |    Month     |     Income     |
----------------------------------------------
----------------------------------------------
|  2012      |    January   |   20,000       |
|  2012      |    February  |   20,000       |
|  2012      |    March     |   20,000       |
|  2012      |    April     |   20,000       |
----------------------------------------------
etc..

任何帮助,建议或一般指示将不胜感激！

我正在阅读http://guides.rubyonrails.org/active_record_querying.html尝试将sql查询转换为正确的Rails查询.

到目前为止,我已经匹配了第二行到最后一行：

AND c.analysiscode <> 213

同

@clinical_income_by_year = Clinical.where("AnalysisCode != 213")

宝贝步骤！

UPDATE

由于Rails指南网站,我现在已经对过滤进行了排序,但我仍然坚持对sql查询进行分组和求和.到目前为止我有以下内容：

@clinical_income_by_year = Clinical.where("AnalysisCode != 213 AND Payments != 0 AND LineBalance != 0").page(params[:page]).per_page(15)

我正在努力构建以下两行的sql查询：

sum(c.LineBalance) as "Income"

和

GROUP BY c.MonthYear;)

我的视图代码如下所示：

<% @clinical_income_by_year.each do |clinical| %>
  <tr>
    <td><%= clinical.TransactionDate.strftime("%Y") %></td>
    <td><%= clinical.TransactionDate.strftime("%B") %></td>
    <td><%= Clinical.sum(:LineBalance) %></td>
  </tr>    
  <% end %>
</table>
  <%= will_paginate @clinical_income_by_year %>

解决方法

@clinical_income_by_year = Clinical.find_by_sql(%q{ ... })

我建议使用％q或％Q(如果你需要插值),这样你就不必担心嵌入式引号了.您还应该将其移动到模型中的类方法中,以防止您的控制器担心不属于他们业务的事情,这也可以让您轻松访问connection.quote和朋友,以便您可以正确使用字符串插值：

find_by_sql(%Q{
    select ...
    from ...
    where x = #{connection.quote(some_string)}
})

另外,SQL中的分号：

GROUP BY c.MonthYear;})

没有必要.有些数据库会让它通过,但无论如何你应该摆脱它.

根据您的数据库,标识符(表名,列名,……)应该不区分大小写(除非一些可恶的人在创建它们时引用它们),这样您就可以使用小写列名来使某些内容适合Rails更好.

另请注意,某些数据库不会喜欢GROUP BY,因为SELECT中的列没有聚合或分组,因此对于每个组使用哪个c.transactiondate存在歧义.

查询的更“Railsy”版本看起来像这样：

@c = Clinical.select(%q{date_format(transactiondate,'%Y') as year,date_format(transactiondate,'%b') as month,sum(LineBalance) as income})
             .where(:payments => 0)
             .where('linebalance <> ?',0)
             .where('analysiscode <> ?',213)
             .group(:monthyear)

然后你可以做这样的事情：

@c.each do |c|
    puts c.year
    puts c.month
    puts c.income
end

访问结果.你可以通过将日期修改推送到Ruby来简化一点：

@c = Clinical.select(%q{c.transactiondate,sum(c.LineBalance) as income})
             .where(:payments => 0)
             .where('linebalance <> ?',213)
             .group(:monthyear)

然后在Ruby中拆分c.transactiondate而不是调用c.year和c.month.

（编辑：李大同）

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