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Welcome to your comprehensive guide to Structured Query Language (SQL) fundamentals, the primary language used to communicate and manipulate databases. This guide is designed for beginners, but also beneficial for those who need a refresher or need to improve their SQL skills.
Introduction to SQL
SQL, pronounced as ‘ess-que-ell’ or ‘sequel,’ stands for Structured Query Language. It is a standard language for managing data held in a relational database management system (RDBMS) or for stream processing in a Relational Data Stream Management System (RDSMS). SQL includes data insertion, query, update and delete, schema creation and modification, and data access control.
SQL Syntax
Although various database systems utilize SQL, most have their additional proprietary extensions that are usually used only on their system. However, the standard SQL commands, such as “Select”, “Insert”, “Update”, “Delete”, “Create”, and “Drop”, can be used to accomplish almost everything that you need to do with a database.
example 1: SELECT Statement
This statement is used to select data from a database. The result is stored in a result table, sometimes called the result-set. Here’s an example of its usage:
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SELECT column1, column2, ... FROM table_name; |
example 2: WHERE Clause
The WHERE clause is used to filter records. It is used to extract only those records that fulfill a specified condition. Here’s an example of its usage:
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SELECT column1, column2, ... FROM table_name WHERE condition; |
example 3: INSERT INTO Statement
This statement is used to insert new records in a table. It is used in the following two forms:
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-- form 1: Insert data in all columns INSERT INTO table_name VALUES (value1, value2, value3, ...); -- form 2: Insert data in specific columns INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); |
By understanding and applying these SQL commands, you are well on your way to mastering SQL. However, keep in mind that practice is key when learning a new programming language. Happy coding!