Delphi / Free Pascal: very simple "old school" mutex

Submitted by st on Mon, 22/07/2013 - 16:28

The code below show how to implement very simple but cross-platform "old school" mutex (mutually exclusive semaphore)

Programming

Delphi |
Free Pascal

Nullables in Free Pascal and Delphi

Submitted by st on Wed, 30/01/2013 - 00:44

An example of generic implementation of nullable value types in FreePascal (easy to adapt for Delphi).

Programming

Delphi |
Free Pascal

Fast inserting a file into a table

Submitted by st on Sat, 01/12/2012 - 11:15

How to insert fast a file (i.e. binary one) from disk to a SQL Server table?

Certainly the SQL Server account should have a corresponding permissions to access the file on the disk. For example I take the file C:\WINDOWS\system32\oembios.bin having the size about 12 MB. For really big files you'd better switch to the FILESTREAM approach.

Programming

SQL Server

SQL: generate date/time series

Submitted by st on Fri, 27/04/2012 - 20:31

There are many examples of user defined table functions generating the series of dates(times) between two specified values. Usually, in OLAP you can see a table filled by the date/time series, too. Such table avoid to generate the values "on the fly".

However, in some cases you may be unable to use an UDF or a table. Fortunately, "pure SQL" method still works.

Suppose, the start and finish dates are specified as entry parameters. The transact SQL code below generates the series "moth by month".

Programming

SQL: delete duplicated rows

Submitted by st 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 st 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 st 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

Indexing columns of bit type

Submitted by st 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

SQL quine (self-reproducing SQL)

Submitted by st on Sat, 30/10/2010 - 14:18

A quine is a computer program which takes no input and produces a copy of its own source code as its only output. The challenge for programmers is to write the shortest code in the given language. Here are my examples in Transact SQL and in ANSI SQL.

Note that we do not take in account the output format printing by any console SQL clients. For example, we are unable to suppress the output of column names or separators in the common case.

Programming

Dynamic result ordering in SQL

Submitted by st 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.

USE AdventureWorks
GO

Programming

SQL Server

Programming