Small and Large Stones of Programming

A simplified database can be handled easily using tie() of Perl, instead of using heavy-duty databases such as relational databases. When using tie(), hashes can be tied to an external database and the hashes can be permanent. However, in contrast to heavy-duty databases, it is not possible to write to the database in parallel and the performance is probably lower. So it is suited for prototypes but not suted for real use.

Microsoft Excel is often used when creating a data group such as a database or data to be entered to a database. So, we often want to enter data created by Excel or another program, for example, by outputting it to a tab-separated text. The following program is an example for such task.

Relational databases are widely used. However, it is not very clear how queries written by SQL are executed by the DBMS. Queries are usually interpreted by DBMS but not compiled into native code. The reason why not compiled into machine code is that it is very important to optimize queries by looking at the properties of tables at run time for the query to be applied. However, in this article, to look at the execution mechanism of queries, I try to simulate them using Perl programs (i.e., “compiled code”).