For an instructor lead, in-depth look at learning SQL click below.
SQL has been a cornerstone of data management and more importantly, data extraction for over 40 years. Structured Query Language, or SQL, is a powerful tool you can learn to use proficiently in a short amount of time and ace your game in data management. This blog post aims to provide a clear, foundational approach to learning SQL for beginners and lead you on your path to becoming a SQL Ninja.
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Understanding SQL
In the simplest terms, SQL is the language that we use to “speak” with a database to fetch and manipulate data. Let’s look at a simple example of SQL.
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SELECT * FROM Books |
This is the basic of SQL – “SELECT * FROM [table-name]” simply retrieves all data from the specified table, in this case, “Books”.
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Getting Started: SELECT, FROM, WHERE
The first concepts beginners need to understand are SELECT, FROM, and WHERE. 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 WHERE clause is used to filter records, and is added after the FROM clause.
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SELECT title, author FROM Books WHERE published_year > 2000 |
In this script, it says to display the book title and author from the Books table that have a publishing year above 2000.
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The Power of Queries: JOIN
As you delve deeper into SQL, you’ll discover the power of JOIN, which lets you connect data from two or more tables. Let’s suppose you have another table, Authors, and you want to list all books along with their author’s details.
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SELECT Books.title, Authors.author_name, Authors.author_country FROM Books INNER JOIN Authors ON Books.author_id = Authors.author_id WHERE Books.published_year > 2000 |
This script will display the title of the books, the name of the authors, and the country of the authors for the books published after the year 2000.
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Transforming Data with SQL
Beyond retrieving data, SQL is an impressive tool for updating and transforming data. Here’s a quick example.
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UPDATE BOOKS SET price = price*0.9 WHERE published_year < 2000 |
This script makes all the books published before the year 2000 go on a 10% sale.
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A Final Note
SQL is a powerful language that, when mastered, can open many doors in the data industry. Remember, the most effective way to learn is by doing, so try writing your SQL scripts and testing different queries to learn and understand the potentials of SQL. Welcome on your journey from being a novice to becoming an SQL Ninja!