![]() ![]() Models can be defined in two equivalent ways in Sequelize: Usually, models have singular names (such as User) while tables have pluralized names (such as Users), although this is fully configurable. This name does not have to be the same name of the table it represents in the database. The model tells Sequelize several things about the entity it represents, such as the name of the table in the database and which columns it has (and their data types).Ī model in Sequelize has a name. In Sequelize, it is a class that extends Model. A model is an abstraction that represents a table in your database. Use stored functions to enhance the modularity and efficiency of SQL statements.In this tutorial you will learn what models are in Sequelize and how to use them.Use the CREATE FUNCTION statement to create a stored function.A stored function is a reusable and encapsulated piece of code in a database that performs a specific task and returns a single value.It’s important to notice that if a stored function contains SQL statements that retrieve data from tables, then you should avoid using it in other SQL statements otherwise, the stored function may slow down the query speed. The following illustrates how to call the GetCustomerLevel() stored procedure: CALL GetCustomerLevel( Code language: SQL (Structured Query Language) ( sql ) call the function SET customerLevel = CustomerLevel(credit) The following statement creates a new stored procedure that calls the CustomerLevel() stored function: DELIMITER $$īEGIN DECLARE credit DEC( 10, 2) DEFAULT 0 The following statement illustrates how to call the CustomerLevel stored function: SELECTĬustomerName Code language: SQL (Structured Query Language) ( sql ) Calling a stored function in a stored procedure Or, you can view all stored functions in the current classicmodels database by using the SHOW FUNCTION STATUS as follows: SHOW FUNCTION STATUS WHERE db = 'classicmodels' Code language: SQL (Structured Query Language) ( sql ) Calling a stored function in an SQL statement Once the function is created, you can view it in MySQL Workbench under the Functions section: The following CREATE FUNCTION statement creates a function that returns the customer level based on credit: DELIMITER $$ĭETERMINISTIC BEGIN DECLARE customerLevel VARCHAR( 20) We will use the customers table in the sample database for the demonstration. Let’s take an example of creating a stored function. Upon reaching the RETURN statement, the stored function terminates the execution of the stored function immediately. Inside the body section, you need to include at least one RETURN statement. The RETURN statement sends a value to the calling programs. If you don’t use DETERMINISTIC or NOT DETERMINISTIC, MySQL defaults to the NOT DETERMINISTIC option.įinally, write the code in the body of the stored function in the BEGIN.END block. Third, specify the data type of the return value in the RETURNS statement, which can be any valid MySQL data types.įourth, determine whether a function is deterministic or not using the DETERMINISTIC keyword.Ī deterministic function always returns the same result for the same input parameters, while a non-deterministic function produces different results for the same input parameters. You cannot specify IN, OUT or INOUT modifiers to parameters Second, list all parameters of the stored function inside the parentheses followed by the function name.īy default, stored functions consider all parameters as IN parameters. DETERMINISTIC BEGIN - statements END $$ĭELIMITER Code language: SQL (Structured Query Language) ( sql )įirst, specify the name of the stored function that you want to create after CREATE FUNCTION keywords. The following illustrates the basic syntax for creating a new stored function: DELIMITER $$ ![]() To create a stored function, you use the CREATE FUNCTION statement. This enhances the readability and maintainability of the procedural code. Unlike a stored procedure, you can use a stored function in SQL statements wherever you use an expression. Typically, you use stored functions to encapsulate common formulas or business rules, making them reusable across SQL statements or other stored programs. Introduction to MySQL Stored FunctionĪ stored function is a specialized type of stored program designed to return a single value. Summary: in this tutorial, you will learn how to create a stored function using the CREATE FUNCTION statement. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |