1. Use The Right Language

Web developers often have a plethora of languages at their disposal. It is crucial for developers to use the proper language for the job.

Let's review the following code. In the first example, the developer is selecting all columns and all rows from the customer table. In the second example, the developer is selecting only the first name, last name and address from the customer table for a single customer with ID 1001. Not only does the second query limit the columns that are returned, it will also perform better.

2. Secure Your Code

Databases store valuable information. Because of this fact, databases are often prime targets for attack. Many developers are unaware that their code has critical security vulnerabilities, which is a very scary fact not only for clients, but also for you. Currently, developers can be held legally accountable if their own personal negligence results in a database security risk that is then exploited.

3. Understand Joins

Single table SQL select statements are rather easy to write. However, business requirements often dictate that more complex queries must be written. For example, "find all orders for each customer, and display the products for each order". Now, in this particular situation, it would be likely that there is a customer table, an order table, and an order_line table (the last would be to resolve a possible many-to-many record relationship). For those who are slightly more familiar with SQL, it is readily apparent that a table join, actually, two table joins will be required for this query. Let's look at some sample code.

4. Know Your Data Types

In SQL, typically each table column has an associated data type. Text, Integer, VarChar, Date, and more, are typically available types for developers to choose from.

5. Write Compliant Code

All programming languages have standards which web developers should be aware, and SQL isn't any different. SQL was standardized by ANSI and then ISO, with new revisions to the language being occasionally submitted. The latest revision is SQL:2008, although the most important revision that developers should be aware of is SQL:1999. The 1999 revision introduced recursive queries, triggers, support for PL/SQL and T-SQL, and a few newer features. It also defined that the JOIN statements be done in the FROM clause, as opposed to the WHERE clause.

When writing code, it is important to keep in mind why standards-compliant code is useful. There are two primary reasons why standards are used. The first is maintainability, and the second is cross-platform standardization. As with desktop applications, it is assumed that websites will have long lifespans, and will go through various updates to add new functionality and repair problems. As any systems analyst will tell you, systems spend a majority of their lifespan in the maintenance phase. When a different programmer accesses your code in 2, 5 or 10 years, will they still be able to understand what your code is doing? Standards and comments are designed to promote maintainability.

The other reason is cross-platform functionality. With CSS, there is currently an ongoing standards battle between Firefox, Internet Explorer, Chrome, and other browsers about the interpretation of code. The reason for the SQL standards is to prevent a similar situation between Oracle, Microsoft and other SQL variants such as MySQL.

6. Normalize Your Data

Database normalization is a technique to organize the contents of databases. Without normalization, database systems can be inaccurate, slow, and inefficient. The community of database professionals developed a series of guidelines for the normalization of databases. Each 'level' of normalization is referred to as a form, and there are 5 forms, total. First normal form is the lowest level of normalization, up to fifth normal form, which is the highest level of normalization.