Monday, July 13, 2009

Extracting Data From MS Sql Server on MacOS

I've had really a rough time lately getting data from legacy systems based on MS Sql Server. In each case I got only the .bak backup file and had to do the rest. The whole thing is a bit easier if you run everything on windows, but as I did the development on Mac I'll cover how to connect to MS Sql from MacOS as well.

Restore database from backup

You will need a windows machine with MS Sql Server running (of course :-) Luckily, you can download it for free from here. Next connect to the database server using the command line utility osql (you will need to have it in your PATH)
cd C:\Program Files\Microsoft SQL Server\MSSQL\Binn
osql -E
You may need to create a new user:
use master
EXEC sp_addlogin 'peter', 'pass45'
Now let's have a look at the backup file (put it in some easy location so you don't have to type out the path):
This query allows us to find out the logical name of the database and log file which is needed to appropriately restore a database to a new path. What you get is basically an original location of the data and the log file. In my case I got:
AMS_Data      D:\Program Files\Microsoft SQL Server 2000\MSSQL\data\AMS_Data.MDF
AMS_Log      D:\Program Files\Microsoft SQL Server 2000\MSSQL\data\AMS_Log.LDF
Which means that the original installation was on drive D:\. As my temp server is on C: I will have to recover with changing the locations of the files
FROM DISK='c:\AMS.bak'
MOVE 'AMS_Data' to 'C:\Program Files\Microsoft SQL Server\MSSQL\Data\ams.mdf',
MOVE 'AMS_Log' to 'C:\Program Files\Microsoft SQL Server\MSSQL\Data\ams_log.ldf'
The only important thing here is that 'AMS_Data' and 'AMS_Log' names match the ones from the previous query. Now you should hopefully see that your database has been restored. Now, will just get access to the database:
use ams
EXEC sp_grantdbaccess 'peter'
sp_addrolemember db_owner,peter
There's more info on how to use osql here. Now we should be set to connect to the database from development machine. This was quite a number of steps just to restore the database - compared to createdb tmp; psql tmp <>Connecting to MS Sql from MacOS We will need to install and set up a couple of things:
sudo port install rb-dbi +dbd_odbc
sudo port install freetds
set up connection to database
Add your server to the end of the file:
 host =
 port = 1433
 tds version = 8.0
where the host is IP of your windows machine. After this step you should be already able to connect to MS Sql Server:
tsql -S Ams -U peter -P pass45
You should get the server database prompt (just like the osql on windows machine). You can try some commands like
use ams
select * from contacts
Now set up ODBC connection. Go to Applications -> Utils -> ODBC Administrator 1) add driver with following descriptions:
Description: TDS
Driver File: /opt/local/lib/
Setup FIle: /opt/local/lib/
Define as:   System
2) add User DNS DSN: Ams Desc: old AMS database server add 2 keyword/value placeholders. To update them click on it and press TAB. Set it to following values:
ServerName: Ams   (or whatever you set in freetds.conf)
Database: ams   (or whatever your database name)
now you should be able to test iODBC. Note that I am using sudo for this as it doesn't seem to work without sudo complaining Data source name not found and no default driver specified. Driver could not be loaded (0) SQLSTATE=IM002.
sudo iodbctest "dsn=Ams;uid=USERNAME;pwd=PASSWORD"
You should be now in interactive terminal again. Once all this works connecting from Ruby is really easy:
require 'rubygems'
require 'dbi'


Rescuing the data

This is just a short ruby script I use to extract all the data from MS Sql and import it to Postgresql. It's not any functional database conversion - it's just to get the data out to something that's easier to work with and doesn't require windows machine running. It may have an issue with binary fields - it worked on most of them but it did choke on a couple of fields. DBI actually provides more metadata like NOT NULL attribute, primary key, etc. so the script could generate a more precise copy of the original database but this was enough for what I needed. You may run into unknown data type - especially if you try to import it to a different database engine - all you need to do is just update the method update_type to return correct mappings of the data types.
require 'rubygems'
require 'dbi'
require_library_or_gem 'pg'

def escape(text)
 return "NULL" if text.nil?

 text = PGconn.escape("#{text}")

 return "'#{text}'"

  def self.update_type(col)
    type = col["type_name"]
    type ||= 'timestamptz'
    type = type.downcase
    case type
    when 'clob'
      return 'varchar'
    when 'varbinary'
      return "oid"
    when 'long varbinary'
      return "oid"
    when 'double'
      return 'double precision'
    when 'tinyint'
      return 'smallint'
    when 'char'
      return "char(#{col['precision']})"
      return type

 dbh = DBI.connect("DBI:ODBC:ams", "peter", "pass45")

 sth = dbh.prepare('select name from sysobjects where type = \'U\' ORDER BY NAME;')
 tables = sth.collect{|row| row[0]}

 tables.each do |table|
   sth = dbh.prepare("select * from #{table} ")

      create = "CREATE TABLE #{table}(\n"
      create << sth.column_info.collect{|col| "\"#{col['name'].downcase}\" #{update_type(col)}"}.join(",\n")
      create << ");\n\n"

      puts create

      sth.each do |row|
        create << "INSERT INTO #{table} (#{sth.column_info.collect{|column| "\"#{column['name'].downcase}\""}.join(', ')}) VALUES (#{sth.column_info.collect{|col| escape(row[col['name']])}.join(', ')});\n"
      create << "\n\n"
      output ="data_ams.sql", "ab+")
      output.puts create
      #puts create
To import the data to Postgresql is as simple as:
createdb ams_backup
psql ams_backup <> noise.txt


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