Function is a predefined program in which we pass the parameters and it return a value. There are two types of function create function and predefined functions.
Create function- Like other languages we can also create function in MySQL.
Below syntax is used to create function:-
CREATE FUNCTION function_name [ (parameter datatype [, parameter datatype]) ]
//parameters are passed into the function
RETURNS return_datatype //function's datatype return the value
BEGIN
declaration_section //declaration of local variables
executable_section //code for the function
END;
Predefined functions- Predefined are the functions which are inbuilt, it only needs to be called. There are various types of predefined functions-Aggregate function, String function, Date and Time and Control flow functions.
1.AGGREGATE FUNCTIONS
| Functions |
Description |
| AVG() |
Finds the average |
| COUNT() |
Counts the number of rows |
| MAX() |
returns the maximum value |
| MIN() |
returns the minimum value |
| SUM() |
returns the sum |
2. STRING FUNCTIONS
| Functions |
Description |
| UCASE() |
Converts the text in upper case |
| LCASE() |
Converts the text in lower case |
| LEN() |
returns the length of text area |
| TRIM() |
removes unwanted character |
| CONCAT() |
concatenate two or more strings into one string |
3.DATE AND TIME FUNCTIONS
| Functions |
Description |
| DATEDIFF() |
Calculates the difference between two dates |
| DATE_FORMAT() |
formats the date into specific format |
| NOW() |
returns the current date and time |
4. CONTROL FLOW FUNCTIONS
| Functions |
Description |
| IF() |
returns the value inside this function |
| IFNULL() |
if it is not null then returns the first argument otherwise returns the second argument |
| NULLIF() |
if both the arguments are equal then returns null, otherwise returns the first argument |
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