MySQL is a hot favourite RDBMS, primarily when developing web applications, and Ruby is an emerging language in the web development business. I have earlier discussed about working with MySQL in many other languages like Python, Perl, C, etc. In this article we will be looking at installation and usage of the MySQL library for Ruby.
Installing MySQL Library for Ruby
Installation is pretty straightforward using Ruby Gems.
Code:
$ gem install mysql
Fetching: mysql-2.9.0.gem (100%)
Building native extensions. This could take a while...
Successfully installed mysql-2.9.0
1 gem installed
Installing ri documentation for mysql-2.9.0...
Installing RDoc documentation for mysql-2.9.0...
You may also install the library from source, but I doubt you would need to do that.
Basic Usage
Basic usage would mean connecting to the database server, issuing queries, read resultset & loop through them. Follow the sample code below to understand the basic usage, I have added comments for ease.
Code: Ruby
#!/usr/bin/ruby
## load gems
require 'rubygems'
## load mysql library
require 'mysql'
## connect to the mysql server
con = Mysql.new('localhost', 'myuser', 'myPas*', 'my_db')
## execute a query
rs = con.query('select * from people')
## loop through the result set
## this returns each row as hash, the field name being the key
rs.each_hash(with_table=false) { |h|
puts h['name']
}
## alternate way to iterate through the result set
n_rows = rs.num_rows
n.rows.times do
puts rs.fetch_row.join(" ")
end
con.close
Advanced Usage
In advanced usage we will look at prepared statements which improve the efficiency and the security, provide features like place holders, and error handling. Unless you are a completely new to programming the sample code below will be more than enough to get you started in enabling database connections in your Ruby program.
Code: Ruby
#!/usr/bin/ruby
require 'rubygems'
require 'mysql'
## block where the code runs, so that the error may be trapped
begin
## connect to the mysql server
con = Mysql.new('localhost', 'myuser', 'myPas*', 'my_db')
## execute a query
prepared_statement = con.prepare('select * from people where age > ?')
prepared_statement.excute 3
## loop through the result set
## this returns each row as hash, the field name being the key
prepared_statement.each { |h|
puts h.join(" ")
}
## clean up
prepared_statement.close if prepared_statement
rescue Mysql::Error => e
## handle/report error
puts e.errno
puts e.error
ensure
## this ensures that the database connection is closed
con.close if con
end
Enjoy coding in Ruby.
