Rails 3 在没有模型的情况下执行自定义 sql 查询
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Rails 3 execute custom sql query without a model
提问by neeraj
I need to write a standalone ruby script that is supposed to deal with database. I used code given below in rails 3
我需要编写一个独立的 ruby 脚本来处理数据库。我在 rails 3 中使用了下面给出的代码
@connection = ActiveRecord::Base.establish_connection(
:adapter => "mysql2",
:host => "localhost",
:database => "siteconfig_development",
:username => "root",
:password => "root123"
)
results = @connection.execute("select * from users")
results.each do |row|
puts row[0]
end
but getting error:-
但出现错误：-
`<main>': undefined method `execute' for #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x00000002867548> (NoMethodError)
what i am missing here?
我在这里缺少什么？
SOLUTION
解决方案
After getting solution from denis-bu i used it following way and that worked too.
从 denis-bu 获得解决方案后，我按照以下方式使用它并且也有效。
@connection = ActiveRecord::Base.establish_connection(
:adapter => "mysql2",
:host => "localhost",
:database => "siteconfig_development",
:username => "root",
:password => "root123"
)
sql = "SELECT * from users"
@result = @connection.connection.execute(sql);
@result.each(:as => :hash) do |row|
puts row["email"]
end
回答by denis-bu
Maybe try this:
也许试试这个：
ActiveRecord::Base.establish_connection(...)
ActiveRecord::Base.connection.execute(...)
回答by Sachin R
connection = ActiveRecord::Base.connection
connection.execute("SQL query")
回答by hajpoj
I'd recommend using ActiveRecord::Base.connection.exec_queryinstead of ActiveRecord::Base.connection.executewhich returns a ActiveRecord::Result(available in rails 3.1+) which is a bit easier to work with.
我建议使用ActiveRecord::Base.connection.exec_query而不是ActiveRecord::Base.connection.execute返回一个ActiveRecord::Result（在rails 3.1+中可用），它更容易使用。
Then you can access it in various the result in various ways like .rows, .each, or .to_hash
然后您可以通过各种方式访问它，例如.rows, .each, 或.to_hash
From the docs:
从文档：
result = ActiveRecord::Base.connection.exec_query('SELECT id, title, body FROM posts')
result # => #<ActiveRecord::Result:0xdeadbeef>
# Get the column names of the result:
result.columns
# => ["id", "title", "body"]
# Get the record values of the result:
result.rows
# => [[1, "title_1", "body_1"],
[2, "title_2", "body_2"],
...
]
# Get an array of hashes representing the result (column => value):
result.to_hash
# => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
{"id" => 2, "title" => "title_2", "body" => "body_2"},
...
]
# ActiveRecord::Result also includes Enumerable.
result.each do |row|
puts row['title'] + " " + row['body']
end
note: copied my answer from here
注意：从这里复制我的答案
回答by montrealmike
You could also use find_by_sql
你也可以使用find_by_sql
# A simple SQL query spanning multiple tables
Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
> [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]
回答by ant
How about this :
这个怎么样 ：
@client = TinyTds::Client.new(
:adapter => 'mysql2',
:host => 'host',
:database => 'siteconfig_development',
:username => 'username',
:password => 'password'
sql = "SELECT * FROM users"
result = @client.execute(sql)
results.each do |row|
puts row[0]
end
You need to have TinyTds gem installed, since you didn't specify it in your question I didn't use Active Record
您需要安装 TinyTds gem，因为您没有在问题中指定它我没有使用 Active Record
