Again, I’ll be digging deeper into all this later in the series. Because the foreign key is configured on the manufacturer_id column, the values in the column must first exist in the manufacturers table. You must execute them in the order specified here so you don’t violate the foreign key defined on the airplanes table. You can execute both statements at the same time or one at a time. For now, all you need to know is that the first statement adds three rows to the manufacturers table, and the second statement adds 10 rows to the airplanes table. I’ll be discussing INSERT statements in more detail later in this series, so I won’t spend a lot of time on them here. To add the database and tables to your MySQL instance, you can run the following SQL code: These are the same tables I created and updated in the previous article in this series. Beyond that, there’s not much else you need to have in place to add a view to a database, other than to be sure you have the permissions necessary to create views and query the underlying tables (a topic I’ll be discussing in more detail later in this series).įor the examples in this article, I created the travel database and added the manufacturers and airplanes tables. Starting with MySQL 8.0.19, the query can instead be a VALUES or TABLE statement, but in most cases, a SELECT statement is used, so that’s the approach I take in this article.Īny tables that are referenced by the SELECT statement must already exist before you can create the view.
The query is typically a SELECT statement that retrieves data from one or more tables. (For a complete rundown on view restrictions and for other information about views, refer to the MySQL documentation on creating views.) Preparing your MySQL environmentĪ view is a stored query that MySQL runs when the view is invoked. It’s not until a user or application tries to invoke the view that MySQL raises the alarm, which could have a severe impact on running workloads. In addition, it’s possible to drop a table that is referenced by a view without generating an error. For instance, MySQL does not let you create an index on a view, define a trigger on a view, or reference a system or user-defined variable in the view’s query. In addition, a view’s ability to abstract schema makes it possible to modify the underlying table definitions without breaking the application.ĭespite the advantages that a view offers, it also comes with a number of limitations. For example, an application developer doesn’t need to create detailed, multi-table joins but can instead invoke the view in a basic SELECT statement. In this sense, the view acts as a virtual table, adding another layer of security that hides the structure of the physical tables.Ī view also helps simplify queries because it presents a less complex version of the schema. Applications invoking the view cannot see how the tables are structured or what other data the tables contain. It abstracts the underlying table schema and restricts access to only the data returned by the view. MySQL stores the view definition as a database object, similar to a table object.Ī view offers several advantages. You can think of a view as a predefined query that MySQL runs when the view is invoked.
Like other database management systems, MySQL lets you create views that enable users and applications to retrieve data without providing them direct access to the underlying tables. To see all 11 items in the series, click here.
#Mysql create view examples series
This article is part of Robert Sheldon's continuing series on Learning MySQL.
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