In SQL tables might have primary keys and indexes. The primary key identifies each record. The key must be unique, it can't be NULL and each table must have just one key. Indexes are something different: they are used to speed up the queries on a specific table. That means we absolutely need indexes on large tables which we often query.
In this short post, I would like to introduce the concept of subqueries in SQL.
A subquery is a query statement inside another query statement. As you already know the order in which a statement is processed is quite important. That is a basic rule like in maths: writing something like 2+2*5 is different than writing (2+2)*5. The first operation gives 12, the second 20.
In SQL the principle is identical.
What is a web page after all? Isn't it a bunch of information linked to something else?
As you know, web sites without links don't exist. And if they exist they are basically dead. When we insert a link in a page, we generally want people to click on it and go somewhere else. However, some times we need to create links that do nothing. Or to better say, links that do not take the user somewhere else.
On the other side, here we are talking about something different. We will see how to use void(0), but we will see something else and we will make some considerations about it.
When naming variables in ASP, we should consider some conventions.
Because the way we write code is quite important for us and, possibly, other people, we do need to keep things as much readable as we can. That means, for example, we should use indents when writing procedures and functions or we should follow a common structure in code blocks.
In general we need to make things easy to read and understand.
That is why there are common naming convention for variables. And in this article we are going to explore them.
Today we are going to see something half way between funny and serious: common mistakes we make while using HTML and CSS.
Why is it funny? Because sometimes those mistakes are so basic that when talking about them we usually react saying we don't make such mistakes. But then... when it happens, for any reason - even the most incredible - the only thing we can do is laugh. Mistakes are always just around the corner. The better we know them, the easier we are going to avoid them.