For an instructor lead, in-depth look at learning SQL click below.
Welcome to this introduction to SQL and relational databases. If you want to dive into the world of data analytics, acquire essential programming skills or understand how large-scale software systems operate, having knowledge of SQL is crucial. SQL (Structured Query Language) is a standard language for managing data held in relational databases. Let’s dive right in.
What is a Relational Database?
A relational database is a collection of data items with pre-defined relationships between them. These items are organized as a set of tables with columns and rows. Tables are used to hold information about the objects to be represented in the database. For example, a University database may contain tables such as Students, Courses, and Lecturers.
Understanding SQL
Structured Query Language (SQL) is a standard language for accessing and manipulating databases. SQL is used to communicate with a database. With SQL, we can create databases, tables, insert, retrieve, and manipulate database data.
Let’s look at the SQL syntax:
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/*Create database*/ CREATE DATABASE database_name; /*CREATE Table*/ CREATE TABLE table_name ( column1 datatype, column2 datatype, column3 datatype, ); /*Insert into table*/ INSERT INTO table_name (column1, column2, column3) VALUES (value1, value2, value3); |
The code above essentially creates a database, a table, and inserts data into the table. These are basic operations that you can do on a database.
Retrieving Data with SQL
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/*Retrieve all data from a table*/ SELECT * FROM table_name; /*Retrieve specific columns from a table*/ SELECT column1, column2 FROM table_name; |
The SELECT command is used to select data from a database. The data returned is stored in a result table, called the result-set.
SQL WHERE Clause
The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition.
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SELECT column1, column2 FROM table_name WHERE condition; |
Started with some basic concepts, I hope this helps to steer you in the right direction. The world of SQL and database management is broad and complex, but it all boils down to storing, manipulating, and retrieving data to provide meaningful information.