Mysql creating stored function
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User defined functions in SQL allow users to save reusable SQL code. Functions can accept parameters and return single values or result sets. They are more limited than stored procedures. Functions are categorized as scalar or table valued depending on whether they return single values or tables. Users create functions using the CREATE FUNCTION statement, which specifies the function name, parameters, return type, and SQL code in the function body.
![Creating stored function
The CREATE FUNCTION statement is used for creating a stored function and user-defined functions
A stored function is a set of SQL statements that perform some operation and return a single value.
Just like Mysql in-built function, it can be called from within a Mysql statement.
The CREATE FUNCTION statement require CREATE ROUTINE database privilege.
Syntax:
The syntax for CREATE FUNCTION statement in Mysql is:
CREATE FUNCTION function_name(func_parameter1, func_parameter2, ..) RETURN
datatype [characteristics] func_body
PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.](https://image.slidesharecdn.com/mysql-creatingstoredfunctionautosaved-200502103521/85/Mysql-creating-stored-function-5-320.jpg)
Mysql creating stored function
- 1. SQL Functions User can create functions in SQL for saving the SQL statements permanently in the system. The functions are calls as User Defined Functions ( UDF ). The UDF is the database object that contains a set of SQL statements. The function accepts input as parameters, performs actions and the result set is returned as action. The return value can be a result set or a single value. The user defined functions has limited functionality as compared to the stored procedures. When user does not require any permanent changes to the database objects, the user defined functions are implemented. Depending on the use, the user defined functions are categorized as scalar functions and table valued functions. PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 2. SQL Functions PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 3. SQL Functions Creating user defined functions The User defined functions contains the following components. 1) The functional name 2) The input parameter and the data type 3) The several options applicable to the input parameter 4) The return parameter type and the optional name 5) The options applicable for the return parameter 6) One or more SQL statements defined by the user The CREATE FUCNTION is used for creating the user defined function PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 4. SQL Functions Functions can be Scalar or Table-valued Basically Scalar returns one value and Table-valued functions (TVF) returns...well a table of results and this are usually found in the FROM clause of a statement. Functions can be Deterministic or Nondeterministic Demerministic = This means they return the same value any time they are called with a specific set of input values. â—¦ i.e SELECT LEN('TEST) will always returns 4 Nondeterministic = different results every time â—¦ i.e SELECT GETDATE() PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 5. Creating stored function The CREATE FUNCTION statement is used for creating a stored function and user-defined functions A stored function is a set of SQL statements that perform some operation and return a single value. Just like Mysql in-built function, it can be called from within a Mysql statement. The CREATE FUNCTION statement require CREATE ROUTINE database privilege. Syntax: The syntax for CREATE FUNCTION statement in Mysql is: CREATE FUNCTION function_name(func_parameter1, func_parameter2, ..) RETURN datatype [characteristics] func_body PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 6. function_name: It is the name by which stored function is called. The name should not be same as native(built_in) function. In order to associate routine explicitly with a specific database function name should be given as database_name.func_name. func_parameter: It is the argument whose value is used by the function inside its body. You can’t specify to these parameters IN, OUT, INOUT. The parameter declaration inside parenthesis is provided as func_parameter type. Here, type represents a valid Mysql datatype. datatype: It is datatype of value returned by function. characteristics: The CREATE FUNCTION statement is accepted only if at least one of the characterisitics { DETERMINISTIC, NO SQL, or READS SQL DATA } is specified in its declaration. Parameters used: PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 7. Function_body is the set of Mysql statements that perform operation. It’s structure is as follows: BEGIN Mysql Statements RETURN expression; END The function body must contain one RETURN statement. PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 8. EMP_ID FNAME LNAME START_DATE 1 Michael Smith 2001-06-22 2 Susan Barker 2002-09-12 3 Robert Tvler 2000-02-09 4 Susan Hawthorne 2002-04-24 Example: Consider following Employee Table- PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 9. We have to find the number of years the employee has been in the company- DELIMITER // CREATE FUNCTION no_of_years(date1 date) RETURNS int DETERMINISTIC BEGIN DECLARE date2 DATE; Select current_date()into date2; RETURN year(date2)-year(date1); END // DELIMITER ; Calling of above function: Select emp_id, fname, lname, no_of_years(start_date) as 'years' from employee; PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.
- 10. EMP_ID FNAME LNAME YEARS 1 Michael Smith 18 2 Susan Barker 17 3 Robert Tvler 19 4 Susan Hawthorne 17 Output PROF.NILESH MAGAR, DR. VISHWANATH KARAD MITWPU.