Fetching result from a SQL query in a 2-D array in Ruby

Question

I have a query in my Ruby file:

@mastertest = connection.execute("select code_ver, date from mastertest")

It treats @mastertest like a 2-D array because, when I print the rows, I get:

@mastertest.each do |row|
puts row[0] : row[1]
end

This prints all code_ver and date from each row.

I am not able to perform any other operations on it. I cannot sort the array nor can I perform a deep copy of the array. I'm guessing it is some MySQL2 type which Ruby considers. How do I convert this to a normal 2-D array?

Couple things to try: Use @mastertest.class to find out what it is. Try using @mastertest.to_a to convert it to an array if it isn't already. — Xavier Holt
– Xavier Holt, Commented Oct 18, 2012 at 18:56
It would help if you told us which library(s) you're using to connect to the database engine. — ian
– ian, Commented Oct 18, 2012 at 19:30
I am using 'mysql' gem to connect to the database.....and I think the result is returned as a mysql result set object. — Pi Horse
– Pi Horse, Commented Oct 18, 2012 at 19:31
@lain That's mysql2 gem. I have answered OP's same question once. Seems he juse didn't tried enough. The class of @mastertest is Mysql2::Result. — halfelf
– halfelf, Commented Oct 18, 2012 at 19:32
@halfelf : I can't find an example which shows me how to use the @mastertest.to_a . It would be helpful if someone can show me an example. — Pi Horse
– Pi Horse, Commented Oct 18, 2012 at 19:38

Prakash Murthy · Accepted Answer · 2012-10-18 19:52:49Z

4

The class of @mastertest is Mysql2::Result ; it provides only each and fields methods

Here's an example for one way to convert the results into a 2-D array:

sql = "select <field1>, <field2> from <table> where <conditions>"
result_array = []

result = ActiveRecord::Base.connection.execute(sql)

index = 0 
result.each do |row|
  result_array[index] = []
  result_array[index] << row[0]
  result_array[index] << row[1]
  ...
  result_array[index] << row[n]
  ...
  index += 1
end

answered Oct 18, 2012 at 19:52

Prakash Murthy

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