#MYSQL CREATE VIEW ALGORITHM HOW TO#

Select first_name, last_name, email from staff where email like check option Here is an example simulated check option Mysql does not offer materialized views, a sort of snapshot of a table, it also does not not offer check constraints however, you can simulate them using the with check option in a view definition. By default the algorithm is set to undefined, which means that MySQL will choose which is most efficient, however merge is more preferred than temptable, however locks on a base table are released when temporary table is generated, which could lead to better performance overall because there is less time spent waiting for locks to be released. The temptable option is specified the view is processed and the output is stored in a temporary table, then the temporary table is used in the query. MySQL has an extension to the standard SQL to help with performance, the algorithm clause specifies which algorithm MySQL will process the view, the merge algorithm option processes a query on a view by merging the query with the view definition.

#MYSQL CREATE VIEW ALGORITHM HOW TO#

I have an example in the above table on how to use sql security.īy default the results of the query are not cached, however it change be changed using the system parameter query_cache, SQL SECURITY DEFINER - use the permissions of the definer who created the view (default).SQL SECURITY INVOKER - use the permissions of the invoker.Views are generally used to allow access to columns on a tables that the user may not have permissions on table, MySQL has added an sql security extension to view data that he/she may not have access too. be careful when using order by if the view already has an order by, strange results may occur.refer to a table that does not exist, although it is possible to drop the table after creating a view.access user variables, system variables, local variables, stored variables or prepared statement parameters.have a derived table (subquery in the from clause).There a a few limitations regarding views Select first_name, last_name from employees # example three, using sql security definer ]Ĭreate view staff_name as select first_name, last_name from employees Ĭreate or replace staff_name as select concat(first_name, ' ', last_name) as full_name from employees Select * from information_schema.views where table_name =' view_name' Views are tools that assist in denormalizing data such as for analysis without change the underlying system, they also allow for simplicity, abstraction, added security and easier schema migration, however they do not improve performance.

Mysql create view algorithm