Monday, January 28. 2013
Continue reading "How to map MS Access auto number to PostgreSQL serial"
This exercise is a continuation of our How to bulk export tables from MS Access and How to recreate MS Access primary keys and indexes in PostgreSQL. As mentioned in the first article, when you use the built-in export feature of MS Access, it exports autonumber fields as integers instead of the more appropriate PostgreSQL pseudo serial type.
The serial type in PostgreSQL is not really a type though, so this behavior is expected. The serial type is really short-hand for defining an integer column and a corresponding sequence object
with a specific naming convention and setting the default value to the next value of the sequence. So this is what we will do in this exercise after we have already exported our data to PostgreSQL. The script we are about to demonstrate will generate an sQL script containing all the
CREATE SEQUENCE, and
ALTER TABLE ALTER COLUMN SET DEFAULT .. needed to convert our integer column to a serial column.
As a side note, Mark mentioned a similar approach to what we've been describing here, but builds all the table , key structures utilizing python. You can check out the python script
Sunday, January 27. 2013
Continue reading "How to recreate MS Access primary keys and indexes in PG"
This exercise is a continuation of our How to bulk export tables from MS Access. Now while this approach will work for other databases besides PostgreSQL, you'll probably need to fiddle with the subroutine to make it work for some other databases. PostgreSQL is fairly ANSI-SQL standard so not too much fiddling should be required to port to SQL Server, MySQL, Oracle etc.
Unlike the prior Visual basic subroutine we showed that exports the tables, this just creates an SQL script that you run on the already created PostgreSQL database that contains the exported data. We didn't test the quote option though we coded it in the subroutine, since like we said we hate having to quote fields. If perchance you are one of those folks that likes to put spaces in your field names to make it more englishy, then you'll need to quote or revise the other routine to convert your spaces to _ or some other thing.
Continue reading "How to bulk export tables from MS Access"
Despite all the nasty things people say about MS Access, it does have fairly database agnostic, easy to use import and export tools and a not too shabby query wizard and query tool. But of course, it's not a server side database so at a certain point won't scale for database storage. You can still use it as a front-end to a server-side database such as PostgreSQL or SQL Server. So once you outgrow it for data storage, you'll probably want a quick way to export your data out. Unfortunately, well at least in the 2003 version, while you can bulk link tables from an ODBC connection, you can only export one table at a time using the "select table" right-click export. In this article we'll show a quick and dirty export MS Access Visual basic sub routine we use to export all tables. This we've only tested on MS Access 2003, so if you are using higher, you might need to customize it a bit. This script should work fine for exporting to any database connection with modification of the connection string.
Sunday, July 01. 2012
Continue reading "Contiguous Ranges of primary keys: a more cross platform and faster approach"
In last article Finding Contiguous primary keys we detailed one of many ways of finding continuous ranges in data, but the approach would only work on higher-end dbs like Oracle 11G, SQL Server 2012, and PostgreSQL 8.4+. Oracle you'd have to replace the EXCEPT I think with MINUS. It wouldn't work on lower Oracle because of use of CTEs. It wouldn't work on lower SQL Server because it uses window LEAD function which wasn't introduced into SQL Server until SQL Server 2012. Someone on reddit provided a Microsoft SQL Server implementation which we found particularly interesting because - it's a bit shorter and it's more cross-platform. You can make it work with minor tweaks on any version of PostgreSQL, MySQL, SQL Server and even MS Access. The only downside I see with this approach is that it uses correlated subqueries which tend to be slower than window functions. I was curious which one would be faster, and to my surprise, this version beats the window one we described in the prior article. It's in fact a bit embarrassing how well this one performs. This one finished in 462 ms on this dataset and the prior one we proposed took 11seconds on this dataset. Without further ado. To test with we created a table:
CREATE TABLE s(n int primary key);
INSERT INTO s(n)
FROM generate_series(1,100000) As n
WHERE n % 200 != 0;
Thursday, October 07. 2010
Continue reading "Universal Unique Identifiers PostgreSQL SQL Server Compare"
Universal Unique Identifiers are 16-byte / 32-hexadecimal digit (with 4 -s for separation)
identifiers standardized by the Open Software Foundation.
The main use as far as databases go is to ensure uniqueness of keys across databases. This is important if you have multiple servers or disperate systems that need to replicate or share
data and each can generate data on its own end. You want some non-centralized mechanism to ensure the ids generated from each server will never overlap.
There are various open standards
for generating these ids and each standard will tie the id based on some unique identifier of the computer or a namespace or just a purely random generator algorithm not tied to anything.
Since this is a question often asked by users coming from Microsoft SQL Server, we will demonstrate in this article the same concept in Microsoft SQL Server and how you would achieve similar functionality in PostgreSQL.
Monday, June 28. 2010
Continue reading "Importing data into PostgreSQL using Open Office Base 3.2"
A while ago we demonstrated how to use Open Office Base to connect to a PostgreSQL server using both the native PostgreSQL SBC and the PostgreSQL JDBC driver.
The routine for doing the same in Open Office Base 3.2 is pretty much the same as it was in the 2.3 incarnation. In this excerpt, we'll demonstrate how to import data into PostgreSQL using Open Office Base, as we had promised to do in
Database Administration, Reporting, and Light Applicaton Development and some stumbling blocks to watch out for.
Command line lovers are probably scratching there head, why you want to do this. After all stumbling your way thru a commandline and typing stuff is much more fun and you can automate it after you are done.
For our needs, we get stupid excel or some other kind of tab delimeted data
from somebody, and we just want to cut and paste that data in our database. These files are usually small (under 5000 records) and the column names are never consistent. We don't want to fiddle with writing code to do these one off type exercises.
For other people, who are used to using GUIs or training people afraid of command lines, the use cases are painfully obvious, so we won't bore you.
Importing Data with Open Office Base Using copy and paste
Open Office has this fantastic feature called Copy and Paste (no kidding), and we will demonstrate in a bit, why their copy and paste is better than Microsoft Access's Copy and Paste particularly when you want to paste into some database other than a Microsoft one.
It is worthy of a metal if I dear say.
Monday, September 07. 2009
Continue reading "Database Administration, Reporting, and Light application development"
One of the most common questions people ask is Which tools work with PostgreSQL. In a sense the measure of a database's
maturity/popularity are the number of vendors willing to produce management and development tools for it. Luckily there are a lot of vendors producing tools for PostgreSQL and the list is growing.
One set of tools people are interested in are Database administration, ER diagramming, Query tools, and quickie application generators (RAD).
For this issue of our product showcase, we will not talk about one product, but several that fit in the aforementioned category.
All the listed products work with PostgreSQL and can be used for database administration and/or architecting or provide some sort of
light reporting/rapid application building suite. By light reporting/application building, we mean
a tool with a simple wizard that a novice can use to build somewhat functional applications in minutes or days. This rules out all-purpose development
things like raw PHP, .NET, Visual Studio, database drivers etc. Things we consider in this realm are things like OpenOffice Base and
MS Access. Most of these tools are either free or have 30-day try before you buy options.
You can't really say one tool is absolutely better than another since each has its own strengths and caters to slightly different audiences and also
you may like the way one tool does one important thing really well, though it may be mediocre in other respects. We also left out a lot of products we are not familiar with and may have gotten
some things wrong.
If we left out your favorite product and you feel it meets these criteria, or you feel we made any errors, please let us know, and we'll add or correct it.
We will be including Free open source as well as proprietary products in this mix. If we left out what you consider an
important criteria, please let us know and we'll try to squeeze it in somewhere.
Sunday, January 04. 2009
Continue reading "How to require all checked conditions are met by a result"
You are developing a consultant search application where by a user looking for a consultant can check all the items in the list they require a consultant to have.
You have 2 tables. consultant and consultant_qual. The consultant_qual has primary key formed by 2 fields consultant_id and qual_id.
qual_id contains a constrained list
with things like 'OpenLayers', 'PostGIS', 'Python', 'C#' etc.
How do you devise a query that given a list of checked options by the user, only returns consultants with not 1 but all of those qualifications?
Wednesday, September 24. 2008
Continue reading "PgAdmin III 1.9 First Glance"
We've been playing around with the snapshot builds of PgAdmin III 1.9 and would like to summarize some
of the new nice features added. PgAdmin III 1.9 has not been released yet, but has a couple of neat features brewing.
For those interested in experimenting with the snapshot builds and src tarballs, you can download them from http://www.pgadmin.org/snapshots/
Tuesday, August 12. 2008
Continue reading "More Aggregate Fun: Who's on First and Who's on Last"
Microsoft Access has these peculiar set of aggregates called First and Last. We try to avoid them because while the concept is useful, we find Microsoft Access's implementation of them
a bit broken. MS Access power users we know moving over to something like MySQL, SQL Server, and PostgreSQL often ask - where's first and where's last?
First we shall go over what exactly these aggregates do in MS Access and how they are different from MIN and MAX and what they should do in an ideal world. Then we shall create our ideal
world in PostgreSQL.
Monday, March 24. 2008
Continue reading "PuTTY for SSH Tunneling to PostgreSQL Server"
What is PuTTY
PuTTY was developed by Simon Tatham and is a very common light-weight MIT-Licensed
free and open source Secure Shell (SSH) client for connecting to Linux/Unix systems via a Teletype (TTY) terminal emulation mode console.
Currently there are ports for Microsoft Windows, other unix like systems,
and ports in progress for Mac OSX and Symbian mobile phone OS.
PuTTY fits into that class of tools we affectionately call Swiss Army Knives because it is
Light, Multi-Purpose, and Good Enough. As an added benefit it is free and open source with a generous license so it is commonly embedded in
PuTTY comes in handy both as an SSH terminal console and as a SSH Tunneling tool which allows you for example
to use PgAdmin III from a local windows workstation against a remote PostgreSQL server even in cases where the linux/unix PostgreSQL pg_hba.conf and postgresql.conf file only allow local connections or non-SSH traffic is blocked by
For more about the nuances
of configuring the pg_hba.conf PostgreSQL server file that controls user access check out Hubert Lubaczewski's “FATAL: Ident authentication failed”, or how cool ideas get bad usage schemas
In this article we shall cover how to use PuTTY's SSH Tunneling feature to access a remote PostgreSQL server that doesn't allow
remote connections. To make it a little more interesting we shall demonstrate how to do this for PgAdmin III.
Wednesday, February 20. 2008
Continue reading "GDAL OGR2OGR for Data Loading"
What is FWTools and OGR GDAL?
FWTools GIS Toolkit is a freely available open source toolkit for Windows and Linux that can do more than GIS tricks.
It is a precompiled bundle of Open Source GIS tools.
The FW comes from the initials of Frank Warmerdam,
the originator of the toolkit and current President of the Open Source Geospatial Foundation (OSGEO).
One key component of the GIS Toolkit is the GDAL/OGR library. Parts of the library have been enhanced by several in the OSGEO community.
GDAL is a basic foundation of countless Open source GIS as well as commercial GIS applications. Here are
Listings of commercial and open source software
that use it and GDAL sponsors.
This is a library which historically has been developed and maintained by Frank Warmerdam, but has started to garner quite a few developers.
GDAL is X/MIT licensed (similar to BSD license), therefore the licensing is very generous for commercial use. The toolkit can be downloaded from
Thursday, January 31. 2008
Continue reading "Using MS Access with PostgreSQL"
Many in the PostgreSQL community use Microsoft Access as a front-end to their PostgreSQL databases.
Although MS Access is strictly a windows application and PostgreSQL has its roots in Unix, the two go well together. A large part of that reason is because
the PostgreSQL ODBC driver is well maintained and has frequent updates. You can expect one new ODBC driver release every 4-6 months. There exist only 32-bit production quality drivers. The 64-bit driver is of alpha quality. In addition to other front-ends to PostgreSQL that utilize the ODBC driver used by Windows developers, there is VB 6 (VB.NET/C# use the ADO.NET driver also very well maintained), Visual FoxPro, Delphi, to name a few).
People who have never used Microsoft Access or anything like it and consider themselves hard-core programmers or database purists, dismiss Microsoft Access as a dangerous child's toy, causing nothing but grief when real programmers and database administrators have to debug the
disorganized mess of amateurs. They dream of the day when this nuisance is rid of and their company can be finally under the strict bureaucratic control of well-designed apps that no one cares to use.
Beneath the croft of this dinkiness/dangerous toy is a RAD and Reporting tool that
can connect to any database with an ODBC or ADO driver. It serves the unique niche of
- Empowering a knowledge worker/beginner programmer/DB user who is slowly discovering the wonders of relational databases and what time savings such a tool can provide.
- On the other side - it is inviting to the pragmatic (lazy) database programmer who has spent precious time to investigate its gems. The pragmatist sees it as a tool which provides a speedy development environment and intuitive reporting environment. It allows one to give more freedom to less experienced users, thus relieving one of tedious requests for information. By using it as a front-end to a strong server-side database such as PostgreSQL, it allows one to enforce a sufficient
level of data integrity and control. The pragmatist realizes that often the best way to maintain order is to not fight disorder because the more you try to restrict
people's freedoms, the craftier they get in devising ways of circumventing your traps.
The pragmatic programmer also takes the view of Give a man a fish and he will pester you for more fish. Teach a man to fish and he will help you catch bigger fish.
Wednesday, January 09. 2008
Continue reading "SQL Math Idiosyncracies"
Question: What is the answer to SELECT 3/2?
Answer: In integer math, it is 1. A lot of people especially those coming from MySQL or MS Access backgrounds are surprised to find out that in PostgreSQL
3/2 = 1. They view this as some sort of bug.
In actuality, the fact that 3/2 = 1 and 1/3 = 0 is part of the ANSI/ISO-SQL standard
that states mathematical operations between two values must be of the same data type of one of the values (not necessarily the same scale and precision though). This is not some idiosyncracy specific to PostgreSQL.
If you try the same operation in SQL Server, SQLite,FireBird, and some other ANSI/ISO SQL compliant databases, you will get the same results. So it seems MySQL and MS Access are the odd-balls in this arena, but arguably more practical.
Tuesday, December 18. 2007
Continue reading "Using OpenOffice Base 2.3.1 with PostgreSQL"
For those who are not familiar with OpenOffice Base. OpenOffice Base is the equivalent of Microsoft Access in the OpenOffice Open source suite. While it is not as feature rich as Microsoft Access, it has been getting increasingly better and has some unique features that even Microsoft Access lacks. Unfortuantely you can't just convert an access mdb to its format like you can with other Open office suite products - Word to Writer Writer to Word etc. However you can open MS Access databases in OOBase, but you can't take advantage of the forms and reports in an MS Access Database.
One thing I always liked about Microsoft Access was the ease with which you could link to various different kinds of datasources and generate rapid queries and so forth. Microsoft Access has a particular feature called Access Projects which ties it very closely with Microsoft SQL Server. What an MS Access Project does is connect you with a specific SQL Server database and allow you to browse all the objects, create forms and reports etc against the objects etc. Unfortunately MS Access Project only works with SQL Server. For other datasources you need to use linked tables and can't make design changes and browse a database as you can with Access Projects.
We had looked at Openoffice Base a while ago and thought they are making progress, but still not quite good enough to put to daily use. When we revisited Open Office Base recently, we were surprised to find a couple of neat nuggets.
- They now had a native SDBC driver for postgresql instead of having to rely on the jdbc or odbc driver. You can still use the jdbc and odbc bridges, and unfortunately for Mac OSX users, you are stuck using the jdbc driver.
- They have this Access Project like feature except it was better than Access in that it worked with other server side dbs. Any that had a driver - e.g. PostgreSQL, MySQL etc.
- It had a relational designer viewer similar to what Access had and when we opened up a PostgreSQL db it laid out all the relationships we had carefully defined before with foreign key constraints etc.
In the next couple of sections we'll lay out how to quickly setup OpenOffice, install the native PostgreSQL driver and JDBC PostgreSQL driver and connect to a PostgreSQL database in OpenOffice Base. Please forgive us for using Windows paths in this.
We figured it would be easier for people to follow since most users coming to this site are windows users and a lot of Linux users already use OO and paths are too different from Linux/Mac OSX installs.