Book Image

MariaDb Essentials

Book Image

MariaDb Essentials

Overview of this book

This book will take you through all the nitty-gritty parts of MariaDB, right from the creation of your database all the way to using MariaDB’s advanced features. At the very beginning, we show you the basics, that is, how to install MariaDB. Then, we walk you through the databases and tables of MariaDB, and introduce SQL in MariaDB. You will learn about all the features that have been added in MariaDB but are absent in MySQL. Moving on, you’ll learn to import and export data, views, virtual columns, and dynamic columns in MariaDB. Then, you’ll get to grips with full-text searches and queries in MariaDb. You’ll also be familiarized with the CONNECT storage engine. At the end of the book, you’ll be introduced to the community of MariaDB.
Table of Contents (10 chapters)
9
Index

Dealing with duplicates and consistency errors


Our product table does not have any UNIQUE index. However, at least one column should contain a unique value; in fact, it would be rather uncommon to have several products with the same name. So, let's add a UNIQUE index:

ALTER TABLE product ADD UNIQUE INDEX unq_name (name);

Now that we have a UNIQUE index, we can use it as an example to discuss how we can deal with duplicates with MariaDB.

Suppose that we want to add a new product, or modify an existing product. In both cases, there is a possibility that the new product name is already in use, causing a conflict. MariaDB supports several statements to automatically handle this conflict:

Syntax

Behavior

INSERT

MariaDB will simply reject the new row with an error that informs us about the problem. If we are inserting several rows with one statement, the whole statement will fail, and no rows will be added.

INSERT IGNORE

Ignore rows that cause an error. They will not be inserted, but all...