Learning SQL For The First Time

Learning SQL For The First Time
December 7, 2022
SQL, which stands for Structured Query Language, is considered a domain-specific programming language. Unlike C++ or Java, it is not a general-purpose programming language. Some argue that it is Turing complete while others do not. MySQL is an open-source relational database management system. MySQL Workbench is an Integrated Development Environment for developing Relational Database Management Systems by coding in SQL. Thanks to Mosh Hamedani's Youtube video titled "MySQL Tutorial for Beginners [Full Course]", I learned how to download and install MySQL Workbench. I found out that there are a lot of necessary steps for installing this software.

A Chinese programmer on Bilibili listed an overwhelmingly wide range of subjects to be learned regarding Java, including Java syntax, JavaWeb, Maven, Spring Boot, etc. When watching the tutorial about JavaWeb, I learned the basic syntax of MySQL, but I have not yet realized the relevance between Java and MySQL. The software recommended for coding in MySQL in this tutorial is called Navicat, but I chose to use MySQL Workbench instead. It is also possible to use command prompt for coding in MySQL, but that is definitely not an ideal environment. Despite an overwhelmingly wide range of subjects to be learned regarding Java, it seems that Swing, a GUI widget toolkit for Java, is not one of them, but I have practiced extensively with loads of GUI classes in Swing for the last few months. Since my most complicated Java program about a Windows 95 simulator has been completed to a certain extent in late November, I would like to expand my programming skill set further. Therefore I tried to learn C++ by following some C++ tutorials, but it turned out to be quite difficult. Regarding C++, there are null pointers and wild pointers to be learned, but even the concept of pointers itself is non-existent in Java.

It seems that MySQL syntax differs greatly from that of C++ or Java. SQL is said to be a declarative programming language, but both C++ and Java are considered to be object-oriented programming languages. Firstly, I found out that MySQL syntax is case insensitive, except for the words enclosed within quotation marks. Secondly, I found out that it is possible to select a specific portion of MySQL code and execute this particular portion instead of the entire MySQL program. For example, I typed the statement "drop table if exists ...(table name)" in the beginning of my first MySQL project. If a MySQL program contains such statements as "create database... (database name)" or "create table... (table name)", then this program as a whole cannot be executed more than once, due to "Error Code: 1050. Table '...(table name)' already exists." Under such circumstances, it is possible to circumvent this error message by executing the statement "drop table if exists ...(table name)", which removes the specified table as a result. Thirdly, I found out that there are a lot of data types in MySQL, such as varchar, tinyint, that are non-existent in object-oriented programming languages such as Java and C++. " Speaking of the basic syntax in MySQL, in order to create a table, firstly it is necessary to type "create table" followed by the name of the table, then an opening parenthesis, then a data named followed by its data type. For the data type varchar, it is necessary to type a number to indicate its maximal length by writing an integer within a pair of parenthesis. A comma should be added after a data name and its data type, except for the last one. After the last data name and its data type, a closing parenthesis and a semicolon should be typed. Then it is possible to display the new table by typing the statement "show tables". Additionally, I found out that "desc" keyword followed by the name of a table is particularly useful. It can be used to display the details of a table.

To put it succinctly, SQL is a programming language for handling data in relational database management systems. Despite their similar functionality in terms of handling data, SQL is probably more sophisticated and useful than Microsoft Excel, as it is possible to define, query, manipulate and control large amounts of data through simple coding instructions. The following code snippet could be regarded as my first SQL project. In MySQL Workbench, a code snippet is called a "script".

drop table if exists object;
create table object(
object_name varchar(10),
object_color varchar(10),
object_counter int,
object_country varchar(20),
object_price varchar(10)
);
show tables;
desc object;
select object_name, object_color, object_counter, object_country, object_price from object;
insert into object(object_name, object_color, object_counter, object_country, object_price)
values("Ball", "blue", 10, "China", "$5"),
("Car", "purple", 3, "Germany", "$20000"),
("Computer", "black", 20, "United States", "$2200"),
("House", "white", 1, "United Kingdom", "$350000"),
...