MySQL Functions can be invoked within expressions and returns a value that is used in place of the function call when the expression is evaluated.
The general the syntax for a MySQL Function call includes the function name followed by parenthesis
Spaces around function arguments are permitted. However, by default there must be no white-space between a function name and the parenthesis following it. This helps the MySQL Parser distinguish between function calls and references to tables or columns that happen to have the same name as a function.
Functions in MySQL Expressions
A function call is a value expression, and can thus appear anywhere where a value expression is accepted. Columns are also perfectly fine to use as arguments as long as they are in the correct data type. A function’s output can also be the input to another MySQL function.
An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for a particular function or operator. Mathematical functions will return NULL on error ( for example; division by zero)
mysql> SELECT 1/0;
| 1/0 |
| NULL |
1 row in set (0.00 sec)
The following are examples of simple functions within a SELECT statement:
The NOW function returns the current date/time.
The VERSION function returns the MySQL version currently being used on the database server host.
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