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Welcome to the exciting world of SQL (Structured Query Language)! This beginner’s guide provides a basic understanding of SQL and its applications in handling and maneuvering around data in a database. SQL is a standard language designed primarily for managing data held in a Relational Database Management System (RDBMS).
What is SQL?
Structured Query Language or SQL is a powerful tool that is used to communicate with and manipulate databases. It is fundamentally used to insert, search, update, delete database records. That doesn’t mean SQL cannot do things beyond that. In fact, SQL is incredibly versatile, and these four operations only scratch the surface of its capabilities.
SQL Syntax
Consider that we have a database table named “Students”. The table looks something like this:
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CREATE TABLE Students ( ID INT PRIMARY KEY, Name VARCHAR (20), Age INT, Grade CHAR (1) ); |
In the above query, we have created a table named “Students” with columns “ID”, “Name”, “Age” and “Grade”.
Select Statement
The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set. The basic syntax is:
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SELECT column1, column2, ... FROM table_name; |
Suppose, you want to select all the students from the “Students” table, you will use the following command:
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SELECT * FROM Students; |
Insert Statement
The INSERT INTO statement is used to insert new records in a table. The basic syntax is:
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INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); |
Let’s insert a new student record into the “Students” table:
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INSERT INTO Students (ID, Name, Age, Grade) VALUES (1, 'John Doe', 14, 'A'); |
Update Statement
The UPDATE statement is used to modify the existing records in a table. The basic usage is as follows:
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UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; |
Let’s update the age of the student “John Doe” in the “Students” table:
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UPDATE Students SET Age = 15 WHERE Name = 'John Doe'; |
Delete Statement
The DELETE statement is used to delete existing records in a table. Here’s the basic syntax:
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DELETE FROM table_name WHERE condition; |
Let’s delete the record of “John Doe” from the “Students” table:
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DELETE FROM Students WHERE Name = 'John Doe'; |
Conclusion
Getting started with SQL is as simple as understanding these basic commands. The key is to practice on any RDBMS platform, like MySQL, SQL Server, or PostgreSQL to get a hands-on grip on these commands. So, what are you waiting for? Dive in and start querying!