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MySQL Articles
Page 66 of 355
How we have multiple stored GENERATED COLUMNS in MySQL table with CREATE TABLE statement?
It is quite possible to add multiple stored generated columns in a MySQL table. It can be illustrated with the following example as follows −Examplemysql> Create table profit1(cost int, price int, profit int AS (price-cost) STORED, price_revised int AS (price-2) STORED); Query OK, 0 rows affected (0.36 sec) mysql> Describe profit1; +---------------+---------+------+-----+---------+------------------+ | Field | Type | Null | Key | Default | Extra | +---------------+---------+------+-----+---------+------------------+ | cost ...
Read MoreHow can we alter table to add MySQL stored GENERATED COLUMNS?
For adding MySQL stored GENERATED COLUMNS in a table, we can use the same syntax as adding a column just adding “AS(expression)” after the data type. Its syntax would be as follows −SyntaxALTER TABLE table_name ADD COLUMN column_name AS(expression)STORED;Examplemysql> ALTER TABLE employee_data_stored ADD COLUMN FULLName Varchar(200) AS (CONCAT_WS(" ", 'First_name', 'Last_name')) STORED; Query OK, 2 rows affected (1.23 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> Describe employee_data_stored; +------------+--------------+------+-----+---------+------------------+ | Field | Type | Null | Key | Default | Extra ...
Read MoreWhat is MySQL GENERATED COLUMN and how to use it while creating a table?
Basically generated columns are a feature that can be used in CREATE TABLE or ALTER TABLE statements and is a way of storing the data without actually sending it through the INSERT or UPDATE clause in SQL. This feature has been added in MySQL 5.7. A generated column works within the table domain. Its syntax would be as follows −Syntaxcolumn_name data_type [GENERATED ALWAYS] AS (expression) [VIRTUAL | STORED] [UNIQUE [KEY]]Here, first of all, specify the column name and its data type.Then add the GENERATED ALWAYS clause to indicate that the column is a generated column.Then, indicate whether the type of ...
Read MoreWhat are the different types of MySQL GENERATED COLUMNS?
We have two types of MYSQL generated columns as follows −VIRTUAL GENERATED COLUMNAs the name suggests, this kind of generated column will not take any disk space. It can be generated with or without using the keyword ‘virtual’. To understand we are illustrating it in the following example −Examplemysql> Create table triangle(SideA DOUBLE, SideB DOUBLE, SideC DOUBLE AS (SQRT(SideA * SideB + SideB * SideB))); Query OK, 0 rows affected (0.44 sec) mysql> Describe Triangle; +-------+--------+------+-----+---------+-------------------+ | Field | Type | Null | Key | Default | Extra | +-------+--------+------+-----+---------+-------------------+ | SideA ...
Read MoreHow can we create MySQL view by selecting data based on pattern matching from base table?
MySQL LIKE operator is used to select data based on pattern matching. Similarly, we can use LIKE operator with views to select particular data based on pattern matching from the base table. To understand this concept we are using the base table ‘student_info’ having the following data −mysql> Select * from Student_info; +------+---------+------------+------------+ | id | Name | Address | Subject | +------+---------+------------+------------+ | 101 | YashPal | Amritsar | History | | 105 | Gaurav | Chandigarh | Literature | ...
Read MoreHow can we use logical operators while creating MySQL views?
MySQL views can be created by using logical operators like AND, OR, and NOT. It can be illustrated with the help of following examples −Views with AND operatorAs we know that logical AND operator compares two expressions and returns true if both the expressions are true. In the following example, we are creating a view which has the conditions based on ‘AND’ operator.ExampleThe base table is Student_info having the following data −mysql> Select * from Student_info; +------+---------+------------+------------+ | id | Name | Address | Subject | +------+---------+------------+------------+ | 101 | YashPal | Amritsar | History ...
Read MoreHow can we create a MySQL view by selecting some range of values from a base table?
As we know that MySQL BETWEEN operator can be used to select values from some range of values. We can use BETWEEN operator along with views to select some range of values from the base table. To understand this concept we are using the base table ‘student_info’ having the following data −mysql> Select * from Student_info; +------+---------+------------+------------+ | id | Name | Address | Subject | +------+---------+------------+------------+ | 101 | YashPal | Amritsar | History | | 105 | Gaurav | ...
Read MoreHow can we create a MySQL view with a subquery?
To illustrate the making of MySQL view with subquery we are using the following data from the table ‘Cars’ −mysql> select * from cars; +------+--------------+---------+ | ID | Name | Price | +------+--------------+---------+ | 1 | Nexa | 750000 | | 2 | Maruti Swift | 450000 | | 3 | BMW | 4450000 | | 4 | VOLVO | 2250000 | | 5 | Alto | 250000 | | 6 | Skoda ...
Read MoreWhere MySQL views can be inconsistent and how can we ensure their consistency?
In case of updateable views, it is quite possible that we update the data that is not visible through the view because we create a view to revealing only the partial data of a table. Such kind of updates makes the view inconsistent. We can ensure the consistency of views by using WITH CHECK OPTION while creating or modifying the views. Although WITH CHECK OPTION clause is an optional part of CREATE VIEW statement but it is very useful to make views consistent.Basically, the WITH CHECK OPTION clause prevents us from updating or inserting the rows which are not visible ...
Read MoreHow can I create a MySQL view that takes the values from a table based on some condition(s)?
If we want to create a view that takes the values from a table based on some particular condition(s) then we have to use WHERE clause while creating the view. The values depending upon the WHERE clause will be stored in view. The syntax of creating a MySQL view with WHERE clause can be as follows −SyntaxCreate View view_name AS Select_statements FROM table WHERE condition(s);ExampleTo illustrate the above concept, we are using the following data from table ‘Student_info’ −mysql> Select * from student_info; +------+---------+------------+------------+ | id | Name | Address | Subject ...
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