For an instructor lead, in-depth look at learning SQL click below.
A critical aspect of any business analytical solution is Data Warehousing. In essence, a data warehouse is a large-capacity repository that sits on the intersection of all the data collected by an organization.
Data Warehousing essentially consolidates data from different sources into one comprehensive database. By merging this data, we’re frequently able to reveal insights that would remain hidden if the data is siloed. And this is where SQL (Structured Query Language) comes into play as the standard language for dealing with data stored in a relational database management system.
The Basics of SQL
SQL language is used to create, manage, and manipulate databases. Here’s an example of SQL code:
|
1 2 3 4 5 6 7 8 9 |
CREATE DATABASE product_data; USE product_data; CREATE TABLE products ( ProductID int, ProductName varchar(255), Price decimal ); |
In the code example above, we are creating a new database called ‘product_data’, then create a new table within this database called ‘products’ including ‘ProductID’, ‘ProductName’, and ‘Price’ as columns.
Extracting Information
We can extract necessary information using SELECT statements. For example, If you want to select all the products from the ‘products’ table, your syntax would be:
|
1 2 3 |
SELECT * FROM products; |
Filtering Data using SQL
One major strength of SQL within data warehousing is its ability to filter data directly from the database. We use WHERE clause to filter the data:
|
1 2 3 |
SELECT * FROM products WHERE Price > 50; |
The above command will return all the products with a price greater than 50.
Joining Tables
In a data warehouse, you may have to work on multiple tables. SQL joins are used to combine rows from two or more tables:
|
1 2 3 4 5 6 |
SELECT Orders.order_num, Products.product_name FROM Orders INNER JOIN Products ON Orders.product_id=Products.product_id; |
The SQL statement above will give us a dataset that consolidates information between Products and Orders.
Conclusion
Understanding how to use SQL for Data Warehousing can give you more control over your business data, helping to deliver better insights and make more data-driven decisions. Remember that the key to effective SQL learning is practice, so always write and test SQL scripts on different databases.