SQL stands for Structured Query Language. It is a set of instructions you use to query databases and extract relevant information based on the needed criteria.
Take for example an SQL query:
SELECT first_name, last_name, student_id, attendance_status FROM attendance_records where attendance_status=1 and date=”01/19/2021”
What does this SQL statement achieve?
It extracts first names, last names, student IDs, and attendance status from a database table called “attendance_records” where the attendance was marked as “1” instead of “0” which means the student was present in the class, and on a selected date.
This SQL query should give you a list of all the students who were present in the class on this particular date.
Before you can understand the nature of a typical SQL query, it is important to have a basic knowledge of how databases are organized and how data is stored in these databases.
And yes, if someone asks you “is SQL a programming language?”, then your answer can be yes, it is. For that, you need to define what is a programming language and we are going to cover that in just a little while. But first, the basics.
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What is data?
Data can be structured and unstructured. Even when the data appears to be unstructured, when you get a bird’s eye view, it begins to appear structured.
Anyway, for data to make any sense, it needs to be structured. By being structured we mean, it must exist in a pattern otherwise it becomes difficult to maintain it in a proper order and even more difficult to get the information you need.
When you maintain an address book, you’re going to have the first name, the last name, the phone number, the email, and the address. The address may be further divided as the house number, the street name, the colony, the landmark, the city, the ZIP Code, the state, and the country.
So, whenever you make a new entry in your address book, you’re most likely to fill up these fields. You may not fill all the fields, but the structure more or less remains the same. This is called a structured database. In a structured database, you always know how many fields are going to be there and what data the individual field contains.
You must have seen an Excel sheet. In a typical Excel sheet, there are rows and there are columns. The columns represent the fields (the data names) and the rows represent the actual records.
Refer to the above example of the attendance_records table database (in a while you will learn the difference between a table and a database). If you put the data in an Excel sheet, first_name, second_name, student_ID, attendance_status, and date will all be separate columns. Then, in individual rows under these respective columns, the actual information will be added.
When data is organized in rows and columns, it is called a table. Every table has rows and columns. A column defines different fields and the rows contain the data for those fields. Since such data can be represented in a tabular form, these datasets are called tables.
There can be different tables in a database.
For example, in a school database, there can be a table that contains just the basic student details such as first name, last name, home address, and grade.
There can be second table to maintain the records of the attendance of individual students.
There can be separate tables for teachers. A separate table for the timetable. A separate table for tracking fee. In fact, there can be hundreds of tables in a school database catering to different needs including finance & bookkeeping, inventory, staff, transport, security, maintenance, stationery, library, and so on.
Why don’t we have just one table? This brings us to the next main topic that we must cover in order to understand SQL.
Why we need relational databases?
As the name suggests, in relational databases we can set up relationships. A typical database can contain millions of records, and sometimes, billions. Maintaining and extracting information from these many records can be mind-boggling and can even fry up computers if the information is not stored properly.
One of the biggest benefits of maintaining relational databases is that they eliminate data redundancy. You don’t enter the same data twice. What does that mean?
In the absence of a relational database, you may have to add everything in a single database, creating lots of repetitive data.
Refer to the same example of maintaining student attendance records. In a school database, you need to maintain all the basic student details such as first name, last name, home address, guardian contact number, date of joining, and the current class he or she is in.
What happens if you want to enter the attendance records of “01/19/2021”?
To assign an attendance status to a particular student, since you’re not maintaining a relational database, you will need to enter all the details and after entering all the details, you will enter the attendance record. Each time you enter the attendance record, you may have to enter all the student details.
Similarly, if a library book is issued to a student, again, since you’re not maintaining a relational database, first you will need to enter all the details of the student and then enter the details about the book that has been issued to the student. Not just the student, you will need to enter all the details of the book as well.
Again, when the student returns the book you will need to enter all the details of the student, as well as of the book.
Suppose you need to assign a student to a class that is going to be taken by a particular teacher and that particular teacher will be taking a book from the library.
You will be entering all the records of the teacher, you will be entering all the records of the student and you will be entering all the records of the book, as well as all the related records.
Multiply this by scores of teachers, thousands of students, and hundreds of thousands of books. You get the point.
What’s the answer?
RDBMS. Relational database management systems.
When you create a student’s table with all the basic details about the student, you assign a unique student ID to that record. The student ID is going to be unique and this particular student ID is not going to be assigned to any other student whether the student is still in the school or not.
Every book in the library database or table is going to have a unique book ID.
Every teacher in the teachers table is going to have a unique teacher ID.
Every class that has been defined in your school system is going to have a unique class ID.
Hence, whenever you need to assign a student to a particular class being taken by a particular teacher who may get a book issued from the library, all you have to do is enter the respective IDs of different entities.
All the tables are related by their IDs. The information attached to these IDs resides in their respective tables and if that information is not needed, it is not retrieved.
All the databases that support SQL commands are relational databases.
What defines a programming language?
To understand MySQL as a programming language, you need to first understand what entails a programming language.
A programming language is a set of instructions that a computer interprets and then takes action guided by those instructions.
To be able to understand these instructions, the computer must be able to understand the language. Also, to be able to provide instructions, the language must be able to understand the architecture of the computer. Hence, there must be a level of understanding on both ends.
This problem is mostly solved when an executable is created. For example, if you write a program in C++, the program is compiled and turned into machine code that is then understood by the machine. Hence, in whichever language you create your program, as long as it is converted into an executable, it can run on a computer.
The same thing is achieved by an interpreter. As long as your interpreter can understand the language, it can interpret the commands and make the computer do its bidding. If you write a program in PHP, which is an interpreter-based language, the interpreter goes through individual commands, interprets those commands to the machine, and the machine executes those commands.
Since, unlike humans, computers cannot speculate, judge, or inferred, you need to give very specific instructions to the computers. If the instructions are not specific, they are not going to work.
Hence, a programming language is a set of instructions written in a manner that those instructions can be understood by the computer.
SQL is also a set of instructions. Above we used the “SELECT” command to retrieve data from the “attendance_records” table.
Now, the SQL interpreter understands the “SELECT” command and you will need to use that command. What if you use “TELL ME”, or “fetch me information about…” or something?
You will get an error. To be able to retrieve data, the SQL interpreter only understands the “SELECT” command.
Also, the “SELECT” command has a well-defined syntax. You need to mention the fields, the name of the database table, and the criteria in a specific order using correct table names, file names, and conditions. If you miss a comma, or if you mixup numeric and alphanumeric fields, for instance, you’re going to get an error.
This is the reason MySQL is called a structured query language. You provide structured queries to the database interpreter and then based on those queries, your commands are executed. This is why SQL is termed as a programming language.
A small history of SQL
In its original form, SQL was called SEQUAL that stands for “Structured English Query Language”. Dr. E. F. Codd originally published a paper titled “A Relational Model of Data for Large Shared Databanks”, which later led to the definition of relational database management systems. IBM was the first company to extensively work on the SEQUEL model. Later, it was renamed as SQL but it is still pronounced as SEQUEL. SQL is the standard RDBMS language used all over the world even for databases that are not relational. For standardization purposes, it is recognized by ANSI.
Two data scientists, Donald Chamberlin and Raymond Boyce developed the first working model of a relational database management system in a company called Relational Software Inc. They released their first commercial relational database management system in 1979. Later, the name of the company was changed to Oracle.
The SQL system version released by IBM was called DB2. In 1987 Microsoft released its own version of an SQL server called MS SQL, in 1987.
One of the most prominent SQL systems used all over the world is called MySQL. It is an open-source system. Once you have installed MySQL on your server, you cannot only create databases and tables, you can also run complete SQL queries.
How is SQL used?
Although we have explained above that SQL is a programming language, you cannot write standalone applications or software using SQL. You use the SQL commands within the software you are building.
Take for example WordPress. It is a blogging platform or a content management system for websites that allows you to manage content by storing that content in a database. For example, if you create a web page or a blog post using WordPress, the title, the URL, the category, and the body text, are all stored in a database, in different tables. When you visit a WordPress link, the link doesn’t exist at that particular time in HTML form. It is generated in real-time by extracting the contents from the database. WordPress completely relies on MySQL.
WordPress is written in PHP. So, MySQL commands, or SQL commands, are issued within the PHP code to make a connection with the database and the respective tables. Then, another set of SQL commands extracts the needed information and displays it to the visitor.
This is one way of using SQL: the SQL queries are embedded within the program you are writing. Different programming languages may have their own way of handling SQL commands but the core SQL queries remain the same, no matter in which language you use them.
If you’re using a mobile app and the app fetches information from a remote database (mostly MySQL) the SQL commands will be embedded within the mobile app code.
The other way is directly using the SQL commands using the SQL Server prompt.
If you’re directly working on a relational database management system, you may have an interface to directly interact with them.
For example, if you have a web hosting account and you can access your MySQL section through your web hosting interface called the cPanel, you will be directed to PHPMyAdmin which is an interface that allows you to directly interact with your MySQL databases. Through this interface, you can run SQL queries.
There is another software that is called Heidi. After you have installed Heidi you will need to connect it to your database server. Once the connection is made, you can easily run all the SQL commands. You can also create and manage databases and their individual tables.
Organizations that use SQL servers have their own individual modes of interacting with their database, mostly through custom-built software.
Is SQL difficult to learn or easy?
SQL is a programming language but unlike other programming languages, you’re not building software using SQL. Having said that, you create batch files using SQL.
Batch files are comparatively smaller programs. As the name goes, the batch files are “batches” of individual SQL commands, organized logically, just the way you would execute them sitting in front of an SQL database console.
Suppose you must execute a series of SQL commands everyday:
- SQL command 1
- SQL command 2
- SQL command 3
- SQL command 22
You need to execute these 22 commands every day in the same order. In such a case, instead of executing these 22 commands in the same order, one by one, you can create a batch file in the same order and then simply execute the batch file. It is normally called a .sql file.
SQL can be difficult to learn or easy to learn, depending on the level of database work you need to do. A relational database system can be quite complicated if you simultaneously need to make connections to multiple tables using an intricate logic.
Generating a report using the query that refers to just one treble can be quite easy. Generating a report using the query that refers to 2 tables can be slightly difficult. As the number of tables increases, so does the complexity of the query.
Suppose you want to run a query that generates a list of houses devastated in the 1988 Hurricane in the Brownsville area of Texas and want to find out the number of people who received a compensation of more than $ 5000. Based on this finding, you want to know in which universities the children of these people studied. We are simply assuming that such information exists in a database.
Hence, it is going to be a complex query. You can see that the language in itself is not difficult but the queries that you need to generate may be baffling sometimes. Therefore, more than how difficult or easy SQL can be, the issue is, how comfortable you are working on intricate logic.
Is it worth learning SQL
Frankly, if you need to use relational database management systems, you need to know SQL. If you want to develop mobile apps that will be connecting to a remote database server, you need to learn SQL. For a data scientist, learning SQL is a must. If you are into big data and you need to analyze lots of complex data, SQL certainly helps. If you’re looking for a job as a database admin or a data analyst, then you must definitely know SQL. Whichever programming language you learn, knowing SQL is a fundamental skill. If you don’t know SQL, you cannot handle databases.
Google, Amazon, Apple, WordPress, Shopify, Netflix and hundreds of thousands of companies use SQL for their everyday data needs. Scientists and researchers use SQL for research and intelligence. Languages rarely come with their own database management commands. Whenever you need to access structured data, you need to embed SQL commands into your ongoing code.
You want to learn SQL if you want to become a business analyst, a data scientist, a software engineer, a database administrator, a quality assurance tester, a researcher, or for that matter, even a journalist. So, yes, it is worth learning SQL if you want to eke out a career in technology.
What are the different flavors of SQL?
As mentioned above, SQL stands for structured query language. In itself, it does not exist. SQL begins to manifest through a database system. Hence, there are multiple SQL database systems with their own strengths and weaknesses.
The most widely used SQL system is MySQL primarily because it is a free source. If you install Apache on your machine, you can automatically install the MySQL server which enables you to create databases and use them for your web applications, software, and mobile apps.
A commercial RDBMS solution is provided by Oracle. In fact, most of the bigger organizations use Oracle for their database needs. You also have Microsoft SQL Server for Windows-based file systems. In the beginning, the MS SQL Server was available only for Windows environment but now they’re also making it available on the UNIX environment. They also call their system as T-SQL which stands for Transaction-SQL.
In the open source category you have PostgreSQL, MySQL and SQLite.
The difference between commercial and open-source SQL systems is that when you go for a commercial SQL system in case you face problems and obstacles, they are taken care of by the vendor. With the open-source solutions, you need to take care of everything including the setup, the interface, and the integration.
Why get SQL homework done online?
There may be multiple reasons why you should get your SQL homework done online. Whether you are aspiring to become an analyst, a database administrator, or a programmer, an online SQL homework service can certainly help you save time and accelerate your learning experience.
Contrary to the popular belief that people get their homework done because they’re not serious about their studies, this is not the case. For example, when you get your SQL homework done online, you may be seeking some clarity that is not available through your classroom books or even from your teacher or professor. When your homework is completed, you can carefully go through it and understand the concepts from a completely different, realistic perspective.
Although homework is given mostly to help you strengthen your understanding, in most cases, a lot of time is wasted trying to figure out how to complete the homework. The learning part is put on the back burner and it is mostly the effort. When you get your SQL homework done online, for example from a service like DoMyProgrammingHomework.io, you solve multiple problems. You increase your understanding of the subject, your homework gets done fast so that you begin to get good grades in your class, and you can use your time constructively.