Rails 3在没有模型的情况下执行定制的 sql 查询

我需要编写一个独立的 Ruby 脚本来处理数据库。我使用了 Rails 3中给出的代码

@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

但是出现了错误:-

`<main>': undefined method `execute' for #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x00000002867548> (NoMethodError)

我错过了什么？

解决方案

从丹尼斯-布那里得到溶液后，我按照下面的方法使用它，也起作用了。

@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
128769 次浏览
小开

How about this :

@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

小开
最佳答案

Maybe try this:

ActiveRecord::Base.establish_connection(...)
ActiveRecord::Base.connection.execute(...)
小开 
connection = ActiveRecord::Base.connection
connection.execute("SQL query")
小开

You could also use 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"}>, ...]
小开

I'd recommend using ActiveRecord::Base.connection.exec_query instead of ActiveRecord::Base.connection.execute which returns a ActiveRecord::Result (available in rails 3.1+) which is a bit easier to work with.

Then you can access it in various the result in various ways like .rows, .each, or .to_hash

From the docs:

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


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