我正在努力将遗留数据库迁移到我的Rails应用程序(3.2.3).原始数据库附带了很多用于报告的长SQL查询.现在,我想做的是在Rails应用程序中使用SQL查询,然后逐个(当时间允许时)将SQL查询交换为“正确的”Rails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;)
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
Ruby解析器不理解sql,您需要使用字符串：
@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.
