The locking mechanism is used to nullify the issue of the conflicts during multiple database connections. INSERT INTO bookview1 (id, name) VALUES (100, "No book 2") – give error and insert will not happen to – not showing newly added data in the view, but in table INSERT INTO bookview (id, name) VALUES (99, "No book") INSERT INTO book (id, name) VALUES (1, "The Thirty-Nine Steps") (id int PRIMARY KEY AUTO_INCREMENT, name varchar(50) NOT NULL) So we can restrict this kind of insertion by adding a check option to that specified query at the time of view creation. If the view is insertable (no join queries and same columns as the main table), and if after insertion in views, newly added rows not showing in views, but showing in the main table, because of the condition added with the specified query at the time of view creation. SELECT c.id AS customer_id, COUNT(*) AS no_of_sale CREATE ALGORITHM = undefined VIEW customer_sales3ĬREATE ALGORITHM = undefined VIEW customer_sales4 merge algorithm, but if it can’t because of an aggregate function over the query to create a view, then switch to the temptable algorithm. With an undefinedone, MySQL uses the best one, i.e. CREATE ALGORITHM = temptable VIEW customer_sales2ĭefault algorithm. With a temptablealgorithm, when a query is executed on the view, every time MySQL creates a temporary table using the query that specified when the view is created and then executed the query on the view. JOIN customers c ON c.id = s.customer_id CREATE ALGORITHM = merge VIEW customer_sales1 Merge algorithm can’t handle aggregate function. With the mergealgorithm, when a query is executed on the view, then that query will combine/merge with the query that is specified when the view is created. Views with Algorithms and Check option Algorithms: It would be invalid to just write film_id since that would make for an ambiguity:ĮRROR 1052 (23000): Column 'film_id' in field list is ambiguous Notice the film.film_id qualification in the SELECT clause with ON. JOIN film_actor ON (film.film_id = film_actor.film_id) WHERE. To illustrate, to do the above with ON, we would have to write: SELECT film.title, film.film_id - film.film_id is required here Īn additional nice treat is that one does not need to fully qualify the joining columns: SELECT film.title, film_id - film_id is not prefixed USING is useful when both tables share a column of the exact same name on which they join. JOIN world.Country ON (City.Countr圜ode = Country.Code) One can join tables ON a column, a set of columns, and even a condition.
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