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Editor to share with you what is the use of the database sql view, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

View introduction

A View is a virtual table that is basically transparent to users who use the view. The view does not actually exist in the database, and the row and column data is used to customize the table used in the query for the view, and is generated dynamically when the view is used.

Define the view

Create view View name as select statement

SELECT * FROM provinces;CREATE VIEW v_pro AS SELECT * FROM provinces;SELECT * FROM vault pro; view view

When you look at the table, you will also list the view chart.

Show tables

Working with View

Select * from v_pro

Delete View

Drop view View name

The role of views

Simplicity: improves reusability, just like a function.

Security: improved security performance, you can set different views for different users.

Data independence: once the structure of the view is determined, you can shield the influence of the table structure change on the user, and adding columns to the source table has no effect on the view; if the source table changes the column name, it can be solved by modifying the view without affecting the visitors.

Modification of the view

The view cannot be modified because of one of the following

The select clause contains distinct

Select sentences contain group functions

The select statement contains a group by clause

The red packet of selecy statement contains an order by clause

The where clause contains related subqueries

There are multiple tables in the from sentence

If there are calculated columns in the view, you cannot update

If a column with a non-null constraint in the base table does not appear in the view definition, the insert operation cannot be done.

These are all the contents of the article "what's the use of database sql views?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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