Exploring common functions

We can use Oracle Supplied functions in our queries. Alternatively, we can create our own functions and later use them in queries. We will learn about functions in the following chapters. In this section, we will explore a few commonly used functions. A complete list of Oracle Supplied functions is out of the scope of this book. You can refer to the Oracle documentation for more details.

Functions in Oracle can be of type scalar or aggregate. Scalar functions operate on a single row whereas the aggregate functions work on multiple rows. In this book we will cover the following Oracle Supplied functions:

UPPER	RPAD	MAX	TO_NUMBER
LOWER	LPAD	MIN	TO_DATE
CONCAT or ("||")	SUBSTR	AVG
LTRIM	COUNT	ADD_MONTHS
RTRIM	SUM	TO_CHAR

The UPPER function converts the character string to uppercase. Similarly, the LOWER function converts a given string to lowercase. The following is a sample query from an HR schema:

SQL> SELECT...