SQL has many built-in functions  .In this course we will be learning about the SQL functions built in into Oracle Database that are available for use in various appropriate SQL statements. There are various types of SQL functions used to perform calculations on data and manipulate other aspects of data within the database.

Understanding SQL functions will help improve your skills and make your work much easier as a database professional. In this course we will be learning about the following types of SQL functions:

Aggregate  Functions
Aggregate functions return a single result row based on groups of rows, rather than on single rows. Aggregate functions can appear in select lists and in ORDER BY and HAVING clauses. They are commonly used with the GROUP BY clause in a SELECT statement, where Oracle Database divides the rows of a queried table or view into groups. In a query containing a GROUP BY clause, the elements of the select list can be aggregate functions, GROUP BY expressions, constants, or expressions involving one of these. Oracle applies the aggregate functions to each group of rows and returns a single result row for each group.

Single Row Functions:
Single-row functions return a single result row for  every row of a queried table or view. These functions  can appear in select lists, WHERE clauses, START WITH and CONNECT BY clauses, and HAVING clauses.

Numeric Functions
Numeric functions accept numeric input and return numeric values. Most numeric functions that return NUMBER values that are accurate to 38 decimal digits

conversion functions 
convert a value from one datatype to another.

Analytic Functions
Analytic functions are commonly used to compute cumulative, moving, centered, and reporting aggregates.
Analytic functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group.