In Built Functions

There are two types of In Built functions in Oracle.

1) Single Row Functions: Single row or Scalar functions return a value for every row that is processed in a query.

2) Group Functions: These functions group the rows of data based on the values returned by the query. The group functions are used to calculate aggregate values like total or average, which return just one total or one average value after processing a group of rows.

Single Row Functions:

There are four types of single row functions. They are:

1) Numeric Functions: These are functions that accept numeric input and return numeric values.

2) Character or Text Functions: These are functions that accept character input and can return both character and number values.

3) Date Functions: These are functions that take values that are of datatype DATE as input and return values of datatype DATE, except for the MONTHS_BETWEEN function, which returns a number.

4) Conversion Functions: These are functions that help us to convert a value in one form to another form. For Example: a null value into an actual value, or a value from one datatype to another datatype like NVL, TO_CHAR, TO_NUMBER, TO_DATE etc.

Note: You can combine more than one function together in an expression. This is known as nesting of functions