Mysql create view examples6/29/2023 ![]() The query starts by creating a temporary result set called top_apps_max. SELECT ga.name, ga.category, ga.rating, tam.max_rating SELECT category, MAX(rating) AS max_rating Here’s a query that accomplishes this goal using a CTE: Specifically, we want information on the maximum rating in each category to be shown next to the rating of the Google app from the same category. ![]() We want to compare the performance of Google apps to that of the top-performing applications in the corresponding categories. We also have the google_apps table, which has the same information for several Google applications: google_apps What Are Common Table Expressions (CTEs) in SQL?Īs you may recall, common table expressions are named temporary result sets that are created using simple SQL statements and then referenced within SELECT, INSERT, UPDATE, or DELETE statements.įor example, let’s say we have a table called top_apps with rating information for top applications across different categories: top_apps This article will walk you through several examples of CTEs and views and explain when to use each one. However, there are some important differences between them. In SQL, both CTEs (common table expressions) and views help organize your queries, leading to cleaner and easier-to-follow code. CTEs: What do they do? How are they different? Which one should you use and when? Get your answers here! You can modify a view by using the ALTER VIEW statement.SQL views vs. Here are two different methods to modify your view. What to do? Create a view! And that view can select only the non-sensitive information from those tables. ![]() But the same tables might also store non-sensitive information that they need to access. Some tables might store sensitive information that the user isn't allowed to access. In other words, we can grant a user access to a view without granting that user access to the underlying tables that the view accesses. This feature means that we can grant users access to some columns of a table but not others (via the view). Rather than being a limitation, this is actually a feature of views. If the "table" doesn't include those columns, you can't query them. As mentioned, the result set of the view is just like a table and some like to call it a "virtual table". We specified the exact columns in the view and those are all that are returned. This is because the view doesn't return the FruitId column. To create a view, type the following statement, followed by the query: The view will immediately be created in your database. You simply preceed your query with one line of code and run it. Create a ViewĬreating views are very simple. But of course, you could also write a complex query against the view if need be. Once it has been saved as a view, you can then run a simple SELECT statement to return the results of the complex query. You could either type this complex query out every time you need to run it, or you could save the query as a view. Therefore, you can query the view as though it was a table.įor example, you could have a complex query that selects data from three different tables. The view could consist of a complex query but it will present the results as though it was a table. ![]() You can then run it later simply by calling that view (rather than writing out the query again). What is a View?Ī view is a query that you save to the database. Some folk refer to views as "virtual tables".Ĭlear as mud? Let's try again. A view is defined as a stored query that when invoked, produces a result set. MySQL provides us with the ability to create views. Here, I explain what MySQL "views" are and how to use them. ![]()
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