Ruby/MySQL SELECT results

ruby-talk
1

Hi

I am playing with Ruby/MySQL, I have everything installed ok. I can
INSERT into my database but I am having trouble with SELECT.

I want to see if the text in the field 'title' has been used before and
if it has return the id of that row. If I run...

require "mysql"
my = Mysql::new("hostname", "username", "password", "db")
hasid = my.query("SELECT id FROM table WHERE title = 'Here is a title'")
puts hasid

I get a result like...

#<Mysql::Result:0x55c74c>

I am expecting just the number in the id field. Any ideas?

Paul

···

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Posted via http://www.ruby-forum.com/.

2

Paul Willis wrote:

Hi

I am playing with Ruby/MySQL, I have everything installed ok. I can
INSERT into my database but I am having trouble with SELECT.

I want to see if the text in the field 'title' has been used before and
if it has return the id of that row. If I run...

require "mysql"
my = Mysql::new("hostname", "username", "password", "db")
hasid = my.query("SELECT id FROM table WHERE title = 'Here is a title'")
puts hasid

I get a result like...

#<Mysql::Result:0x55c74c>

I am expecting just the number in the id field. Any ideas?

hasid.each do |row|
   puts row
end

Keep in mind, that Ruby/MySQL doesn't "rewind" after using an iterator.

I've circumvented that by doing the following:

array = Array.new
hasid.each do |row|
   array.push(row)
end

I haven't tested the code, but it mirrors the code I use, sans implementation details special to my program.

···

--
Phillip "CynicalRyan" Gawlowski

Rule of Open-Source Programming #9:

Give me refactoring or give me death!

3

hasid,=my.query("SELECT id FROM table WHERE title = 'Here is a
title'").fetch_row

fetch_row gives you an array with the row in it.

by putting several variables with commas between them, you can unpack the
array into those variables -- if there's only one element, you can
achieve the same behavior by specifying one variable to assign to,
followed by a comma.

This approach leaves a MySQL::Result object lying around waiting to be
garbage collected before it is closed. This may be wasteful --
personally, I prefer to use DBI instead of MySQL directly, and DBI has a
good way to take care of this cleanup automatically:

require 'dbi'
dbh=DBI.connect('DBI:mysql:db:hostname','username','password')
hasid,=dbh.select_one("SELECT id FROM table WHERE title = 'Here is a
title'")
puts hasid

···

On Mon, 26 Mar 2007 22:19:04 +0900, Paul Willis wrote:

Hi

I am playing with Ruby/MySQL, I have everything installed ok. I can
INSERT into my database but I am having trouble with SELECT.

I want to see if the text in the field 'title' has been used before and
if it has return the id of that row. If I run...

require "mysql"
my = Mysql::new("hostname", "username", "password", "db")
hasid = my.query("SELECT id FROM table WHERE
   title = 'Here is a title'")
puts hasid

I get a result like...

#<Mysql::Result:0x55c74c>

I am expecting just the number in the id field. Any ideas?

Paul

--
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/

4

hasid = my.query("SELECT id FROM table WHERE title = 'Here is a title'")
puts hasid

I get a result like...

#<Mysql::Result:0x55c74c>

I am expecting just the number in the id field. Any ideas?

hasid.each do |row|
   puts row
end

Keep in mind, that Ruby/MySQL doesn't "rewind" after using an iterator.

I've circumvented that by doing the following:

array = Array.new
hasid.each do |row|
   array.push(row)
end

I'm having trouble getting my id out of the array to use as a variable
in an if/then/else statement

I want to get the id (there will only be one in the MySQL database that
matches my query, and then do something like...

if hasid > 0
then
  puts "already here with id " +hasid
else
  puts "this will be a new item"
end

···

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Posted via http://www.ruby-forum.com/\.

5

Paul Willis wrote:

I'm having trouble getting my id out of the array to use as a variable in an if/then/else statement

I want to get the id (there will only be one in the MySQL database that matches my query, and then do something like...

if hasid > 0
then
  puts "already here with id " +hasid
else
  puts "this will be a new item"
end

Try the Mysql::Result#fetch_field_direct method. This should do what you want. At least it did when I played with it in irb.

···

--
Phillip "CynicalRyan" Gawlowski

Rule of Open-Source Programming #6:

The user is always right unless proven otherwise by the developer.