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Welcome to this beginner’s guide to Structured Query Language, or SQL (pronounced “sequel”). This versatile little language lies at the core of many data-driven industries, providing a powerful and efficient means to access, create, manipulate, and manage data in databases. Join us as we delve into the basics and set you up with a solid foundation in SQL.
What is SQL?
SQL is a programming language used to communicate with and manipulate databases. It is particularly effective with relational databases, such as those used by large companies and organizations around the world.
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/* Here is a basic example of SQL syntax */ SELECT column1, column2 FROM table_name WHERE condition; |
SQL Basics
All SQL queries perform some type of data operation such as SELECT, INSERT, UPDATE, DELETE, ALTER, or CREATE. These operations, called “queries”, are the bricks with which SQL is built.
Selecting Data
The most common operation, SELECT, retrieves data from the database. See this example below:
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/* This SQL statement selects the "CustomerName" and "City" columns from the "Customers" table */ SELECT CustomerName, City FROM Customers; |
Inserting Data
The INSERT INTO statement allows you to insert new data into a database. See the example:
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/* This SQL statement inserts a new record into the "Customers" table */ INSERT INTO Customers (CustomerId, CustomerName, ContactName, Country) VALUES ('4', 'Cardinal', 'Tom B. Erichsen', 'Norway'); |
Updating Data
The UPDATE statement allows you to modify data in a database. See this example:
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/* This SQL statement updates the "ContactName" column of the "Customers" table for all records where "CustomerID" equals 1 */ UPDATE Customers SET ContactName='Alfred Schmidt' WHERE CustomerID=1; |
Deleting Data
The DELETE statement enables you to delete data from a database. For example:
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/* This SQL statement deletes all records from the "Customers" table where "CustomerID" equals 1 */ DELETE FROM Customers WHERE CustomerID=1; |
Conclusion
SQL is the lifeblood of data-driven processes. It’s a vast and complex language, but hopefully, this brief introduction has given you a grasp of the basics and encouraged you to learn more. With time and practice, you can become competent, even masterful, in writing and understanding SQL queries.