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Welcome to our SQL guide for beginners. This guide aims to make SQL easy for you, covering basic concepts and commands using practical examples and code snippets. By the end of this tutorial, you’re expected to write simple, yet effective SQL queries.
Introduction
SQL, or Structured Query Language, is a standard programming language for relational databases. It is used to retrieve, delete, insert, and update data in databases. Apart from being standard in nature, it is universally accepted and used, making it a must-have skill for anyone in data analytics or data science.
Basic SQL Commands
Here are some basic commands :
SELECT
The SELECT statement is used to select data from a database. The data returned are stored in a result table, called the result-set. Here is a simple snippet:
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SELECT * FROM Students; |
This command will select all records from the Students table. The asterisk (*) is used to select all columns.
INSERT INTO
The INSERT INTO statement is used to insert new records in a table. Here’s an example:
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INSERT INTO Students (StudentID, LastName, FirstName, Major) VALUES ('1', 'Smith', 'John', 'Computer Science'); |
This command will insert a new record into the Students table.
UPDATE
The UPDATE statement is used to modify the existing records in a table:
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UPDATE Students SET Major = 'Mathematics' WHERE StudentID = '1'; |
This updates John Smith’s major to Mathematics.
DELETE
The DELETE statement is used to delete existing records in a table:
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DELETE FROM Students WHERE StudentID = '1'; |
This removes John Smith from the Students table.
Conclusion
As you can see, SQL isn’t as intimidating as it might seem! These basic commands form the backbone of any database manipulation you would want to perform. As you continue to normalize your database and work with more sophisticated data, you will find that SQL is an indispensable tool in your skillset. Stick with it, and you’ll reap its rewards!