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: #!/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: #!/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.
