SQL: delete duplicated rows

Submitted by Serguei_Tarassov on Fri, 09/03/2012 - 16:17

How to delete the rows having the duplicated values of one or more columns and considered as duplicates? The example in Transact SQL is below.

Programming

SQL Server

Transact SQL: exporting table or view in CSV

Submitted by Serguei_Tarassov on Mon, 20/02/2012 - 12:38

It's pretty easy on SQL Server but pay attention to the database/server rights of used connection. Usually, the preparing like sp_configure requires a system administrator privileges.

Programming

SQL Server

DateTime in C++

Submitted by Serguei_Tarassov on Sat, 04/12/2010 - 13:48

Many years ago we had a need to manipulate the data of types "date" and "time" (DateTime in C# and Delphi/C++Builder). I had developed the corresponding class for these purposes.

Here is the interface with comments:

Programming

GUI: evolution of descriptions

Submitted by Serguei_Tarassov on Thu, 02/12/2010 - 11:37

Let's see one simple example showing how the methods and the languages of graphical user interface (GUI) description are progressing (or regressing, it depends) during the last 15-20 years.

The primitive form description requires:

Indexing columns of bit type

Submitted by Serguei_Tarassov on Wed, 24/11/2010 - 20:06

Clearly, an index build on only one column of the bit type is useless because the selectivity is poor (50% of a table in average). However, when a table has several columns of the bit type, the composite index may be efficient.

For the test example, we'll create a table and fill it with random data.

Programming

SQL Server

Dynamic filtering with SQL

Submitted by Serguei_Tarassov on Mon, 15/11/2010 - 18:45

The one of the most frequent asked question in database development is "How to filter the data returned by a query according to some user selected criteria?". To complete the solution with dynamic ordering see my other blog post.

For every method template I will add icons indicating corresponding advantages and drawbacks.

SQL Server

Dynamic result ordering in SQL

Submitted by Serguei_Tarassov on Tue, 18/05/2010 - 17:19

There are several methods to implement the dynamic ordering of result returned by SQL query. The examples of stored procedures below use the Microsoft's demo database AdventureWorks.