9 helpful SQL tips to create and maintain a top-notch database

What is SQL, and what is it used for?

SQL is a programming language that is often pronounced "sequel." It is used to manage data in a relational database management system (RDBMS) or to process data streams in an RDSMS. Today, it has become a standard language for accessing and manipulating databases.

RDBMS is the foundation for SQL and all modern database systems, including MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. The data in an RDBMS, like most databases, is stored in database objects called tables.

In case you are unaware, a table is a list of data entries related to each other. It is made up of columns and rows, like Excel spreadsheets. But more on databases in the next section.

SQL works exceptionally well with structured data, with relationships between entities and variables. For example, SQL is better than older read-write APIs like ISAM and VSAM in two main ways.

First, it provides an efficient way for users to access many records with just one command. Second, it eliminates the need to indicate specifically how to get to a record, like with an index or without one.

In the 1970s, IBM researchers Raymond Boyce and Donald Chamberlin developed the SQL language. In 1970, Edgar Frank Codd wrote a paper called "A Relational Model of Data for Large Shared Data Banks." This led to the creation of the programming language, which was called 'SEQUEL' at the time.

Codd's paper explained that all the data in a database should be shown as relationships. Boyce and Chamberlin came up with SQL based on this idea.

Malcolm Coxall writes in Oracle Quick Guides (Cornelio Books, 2013) that the first version of SQL was made to work with and get data from System R, IBM's first relational database management system.

But it wasn't until many years later that the SQL language was made available to the public. In 1979, a company called Relational Software, which later changed its name to Oracle, sold Oracle V2, its version of SQL.

The scope of SQL includes data query, data manipulation (insert, update, and delete), data definition (schema creation and modification), and data access control. SQL is mostly a declarative language (4GL) but also has procedural parts. This means that it specifies what is to be done rather than how to do it.

The American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) made SQL a standard in 1986 and 1987, respectively.

Since then, the standard has been changed to add more features. Even though there are standards, most SQL code needs to be changed in some way before it can be moved to a different database system.

What is a database?

A database is a collection of information that has been organized to make it simple to access, administer, and modify. Groups of data records or files, such as sales transactions, customer information, financial data, and product information, are typically stored in computer databases.

Databases store, manage and provided access to just about any kind of information. They collect data on people, places, or things. That information is put in one place and organized so it can be looked at and studied. You can think of a database as an organized group of data.

Databases have existed since the 1960s in a variety of forms; therefore, they are not a recent innovation. Each record in these early databases was connected to numerous other primary and secondary records through a network-style organization.

Relational databases first came into being in around the 1970s, and in the 1980s, the next evolution in the technology was made with object-oriented databases, or Object Database Management Systems (ODBMS). Structured Query Language (SQL), NoSQL, and cloud databases are all used today.

Databases underpin many aspects of our modern world, and chances are most websites you visit will have some form of a database behind the scenes storing and recalling data. Many modern websites will use a Content Management System (CMS) that is, in effect, a very fancy database at its core.

Databases are potent tools and have been employed by many different businesses for many years to help get insights into their business to improve efficiency or help make forecasts and decisions for the future.

They are also handy for storing information on customers, suppliers, etc., that can be accessed, analyzed, and manipulated to improve a business's customer service. For example, social media platforms store information about their users, like their names, email addresses, and how they use the forum, in databases.

There are so many database applications that are impossible to list here, but rest assured, they are an integral part of our modern digital world. For this reason, having specialized experts in managing them is a highly sought and potentially lucrative career choice.

If so desired, you can also go the whole hog and get yourself officially certified in SQL. Some examples include, but are not limited to:

• MySQL Certification — MySQL
• Oracle Database SQL Certified Associate — Oracle University
• PostgreSQL Certification — Enterprise DB

How do you install SQL?

The first thing to understand is that SQL is a database querying programming language that can be written for free using something as simple as a basic word processor or webpage. But, any SQL code you write will be effectively useless without an actual database to connect to.

What people mean when they ask this kind of question is how you install the actual database to store and query using SQL. However, this distinction has become murky in recent years with the extensive proliferation of SQL-based relational databases that can be accessed for free or bought off the shelf.

With an actual database program, there are hundreds to choose from today. Microsoft's SQL Server is one of the most popular and free choices.

It is free to download and install on any Windows Operating System and is relatively easy to set up. It is also one of the most stable and comes with a user-friendly, mature, and regularly updated graphical user interface.

However, as with all Microsoft programs, make sure you choose a more recent version, as they tend to discontinue support for older versions.

If you want a database on your website, your website host will usually have an option to install a SQL database for free as part of your package. That being said, there are many other, typically open-source, options for SQL-based databases.

According to site guru999, some of the best choices are as follows: -

• InterBase.
• Microsoft SQL (as previously mentioned).
• Database Performance Analyzer.
• MySQL (this is by far one of the most popular and widely available).
• PostgreSQL.
• MongoDB.
• OrientDB.
• MariaDB.

Which one you choose will be utterly dependent on your needs and level of expertise in hosting a database online or locally.

Is SQL easy to learn?

Just like Microsoft's Visual Basic (VBA), SQL is a relatively simple coding language that is only as hard as you make it. If you learn the fundamentals and, most importantly, apply them to real projects, your mastery of them will be directly related to the effort you put in.

If you are after some rough time scales, according to the University of Berkeley, you can expect to learn the basics of SQL in about two to three weeks. However, you'll probably need a higher level of fluency if you want to use SQL skills at work.

Trying to learn SQL on your own might take about six months or even longer if you don't use SQL often. You can speed up the process through a formal, intensive learning program like a coding Bootcamp. If you sign up for one of these, you could master SQL in as little as three months.

Whichever route you choose, like any programming language you want to pick up, make sure you build some real projects to apply your knowledge.

What are some must-know tips and hints for SQL?

SQL is a great way to handle data and isn't tricky to master. But, like anything you ever do, it doesn't hurt to take tips and tricks from people more experienced than you.

Before we get stuck in, since SQL and databases are intimately related, our tips and hints will combine a blend of the two.

1. Avoid using spaces in table and field names

When you first set up your database (whichever one you choose), select the table and field names wisely. Ensure they are descriptive and intuitive and avoid multiple-word names. For example, if a table will store the names and addresses of customers, call the table something obvious, and make sure each column (aka field) in the table is also easily identifiable.

"Field 1," "Field 2," etc., are impossible to remember in the future, so give them simple names like "Name," "Surname," etc.

Since you will be calling them frequently when building your SQL queries later, you might make things easier for yourself later down the line.

With regards to multiple-word names, this can create a severe headache later down the line, especially when using APIs to query a database. You will often need to enclose the table name (or field) in square brackets, or the query will fail.

If you need t have multiple words, separate them using an underscore instead. For example, call a field Customer_Name instead of Customer Name.

2. Stick to the "order of execution" in SQL religiously

Another important concept in SQL is something called the "order of execution." This term refers to the way programming clauses are listed in a query.

It is a very simple thing to remember, and failing to do so can lead to problems when attempting to run a query. You can think of it as the correct order of instructions in a dish recipe.

For reference, the order of execution in SQL is as follows: -

• FROM or JOIN (this defines which table(s) you want to access)
• WHERE (This is the SQL clause to filter data)
• GROUP BY (This is the clause to aggregate or group data)
• HAVING (this filters a GROUP BY data set)
• SELECT (This clause is required actually to display the data)
• ORDER BY (This sorts the data for ease of reference)
• LIMIT/OFFSET (These clauses obviously limit the number of rows returned. OFFSET lets you skip certain rows if needed)

Getting any of these out of order can seriously mess up your SQL query results, if it runs at all.

3. Make your code easy to read and follow

In the world of programming, there is something of a cardinal rule to make sure your code is legible and easy to follow. SQL, of course, is not different.

Technically known as formatting, this is a way to make your code look nice, but it doesn't change the results. It also makes your code easier to fix and digest if something goes wrong.

Everyone has a favorite way of putting things together. Still, your employer may have set procedures and format styles, so make sure you follow those to the letter (literally and figuratively).

To see what we mean, take the following example: -

SELECT * FROM `WondersWorld` WHERE `Country` = `Egypt`;

This can also be written like this: -

SELECT

*

FROM

`WondersWorld`

WHERE

Country = `Egypt`;

*Note above that the table and column names are enclosed in backticks here. This tends to be required for some MySQL databases, but not always. It is best to refer to requirements set by your web hosting provider as it can throw errors.

Which one is better is a personal choice, and for small queries like this possibly a little pedantic. But for larger queries, like updating or inserting new rows, where the query can be hundreds of characters long and/or contain hundreds of fields (columns), it can make a big difference when debugging.

It is also generally considered good practice to use Upper and Lowercase letterings in your queries. While SQL clauses aren't case sensitive, ensuring that you stick to either or for the names of things like tables, columns, field values, etc.

Again, this makes debugging your code a little bit easier.

4. Be consistent with your table structure nomenclature

One of the most important principles in any relational database is something called a primary key. This is a special column (or set of columns) in a relational database table used to identify each table record.

A primary key is a unique identifier used to quickly sort through the data in a table. Usually, you can only have a single primary key field in a table.

Primary keys usually: -

• Must have a value that is different for each row of data. The database can automate this to increment by 1 for each new record.
• Cannot contain null values. Since they are the unique identifier for the record, the record usually cannot be saved if it has no value.

A primary key could use one or more fields that are already in the underlying data model, or it could be a special field that is added just for that purpose. Primary keys can then be referred to in other tables to identify a record and store data in a record.

A "foreign key" is a field (or fields) in one table that refers to the primary key in another table. This kind of structure is ideal for things like data entry that includes fields that are drop-downs or a selection of set results. Examples of a foreign key could include a person's sex, country of birth, number of stories in a building, etc.

There are many ways to name primary keys, but the most common is to call it something like "ID" or "id." Foreign keys are usually labeled something like "tablename.id" for ease of reference.

If that all sounds a little confusing, look at the image above. If we take the "Order" table, the "OrderID" will be the primary key, and "SalemanID" would be an example of a foreign ID. "SalemanID" refers to the column of the same name in the table "Saleman" and is also its primary key.

Be consistent with how you name things, and give columns that are foreign keys to other tables clear names. For example, if the column "owner id" is the foreign key to a table called "users," you should call it "user owner id" or something else that makes it clear that it's a foreign key to a certain table.

5. Try to limit the number of tables needed for your project

While there is technically no real limit to the number of tables you can have in a relational database (the maximum number of "permanent" is usually set to 67,108,863), it is best to be as efficient as possible when creating them. Try to plan the fewest number required and consider which data types can be combined into a single table.

Things like dates or postcodes/zipcodes don't need to have their own one or two-column tables with indexes and can instead be added to other tables.

This is called database normalization, and can be a double-edged sword if you go crazy with it.

Limiting the number of tables to work with (and table duplication) will make your SQL database much faster and more efficient when returning queries.

Likewise, try to avoid condensing your tables to several very long multiple-column ones, if possible. Tables with hundreds of columns can be nye on impossible to manage later down the line and can bloat the database as it tends to introduce unnecessary data duplication.

You should also look to find ways to limit string columns as much as reasonably practicable. If one column uses a set of standard values (like months of the year), consider ripping that out into its own table and use it as a lookup to store the index key of the month rather than as a string of letters.

But again, don't go OTT. It is a fine balance.

6. Dates can be a nightmare in SQL, so make things easy on yourself from the off

As great as SQL and SQL-based databases are, simple things like dates can be an absolute nightmare to manage at times. This is especially true if you have a SQL database (backend) connected to third-party software like MS Access or other API frontends.

You may have to convert the date format to store the data in an SQL database correctly, so bear this in mind when building your system.

The first thing to be aware of is that SQL databases tend to store dates as Year-Month-Day or YYYY-MM-DD. Some theme versions have date formats that include the time to or the year, but DATE or DATETIME is the most commonly used and required.

If you can avoid it, try not to break up raw data records into days, months, and years but rather store the whole data as a single field. You can always manipulate the data later when devising your SQL queries.

Some SQL veterans advise that you store dates in the UTC timezone, but this is entirely up to you. For things like dates and time stamps (usually used to record when a row was created or edited), keeping it in the same timezone is invaluable for eliminating series analysis issues.

7. Make good use of temporary tables

Temporary tables are a great way to modify, delete, or store data before "saving" it to your "real" tables. Making clever use of them speeds up your database and is a good idea when working with large datasets.

Using them helps preserve the integrity of your database but is also a great way to "clean" data before committing it to a dataset. One primary use of them is to verify and check data collected from publically accessible data entry forms on a website.

While most users will be genuine, something called SQL injection is a real growing problem from hackers. By storing your data in a temporary table, you can check it and remove any potentially dangerous chunks of text that could severely damage your precious database.

They are also handy for applications built online that may depend on an internet connection. If a connection is lost, the data can be saved in a temporary table and saved later for "real" once a connection is reestablished. They can also store temporary data like login credentials, etc.

Temporary tables can also be created and deleted on demand without affecting other tables on the database. What's not to like?

8. Make sure you are familiar with data types

In SQL, each column in a table usually has a data type associated with it. These typically include common types like Text, Integer, VarChar, Date, and more.

Make sure you choose the right data type for each column when you're developing. Primary keys should always be integers, for example.

It might sound obvious, but dates should be stored in DATE variables, numbers in numeric types, and so on. But with numbers, you have several options, including integer, float, double, etc. They are not the same, so learn what is needed.

Not getting this right can cause unexpected outcomes when you analyze numbers or manipulate data. The outcomes might confuse you as your result will suddenly have decimal places (or vice versa) for no apparent reason.

Attempting to multiply text with integers will also tend to throw an error.

9. Try not to use another developer's code

First, there is absolutely nothing wrong with researching and looking at other people's codes. If you are entirely at a loss or a newbie, this is the best way to learn the syntax of a particular SQL clause or query.

Online forums and sites like Stack Overflow are great places with great communities of experienced developers who are more than happy to share their experiences and insight. Experienced developers are also a valuable resource to sense check your code to make it work or make it more efficient.

However, relying on this too much will stifle your development as a developer and,m frankly, will make you lazy. By grinding the hard way, you will become an unstoppable SQL developer and learn a set of skills that will prove invaluable down the line.

It will also make you quicker when developing your SQL code, as you won't constantly be hitting a wall and looking for spoon-fed solutions.

And that is your lot for today.

SQL is a potent tool if you work with relational databases. So, if you are just a beginner or a little rusty, you might want to implement some of these handy tips. Happy SQL-ing!