A function is a routine that can be invoked from within other SQL statements and returns a value or a table. For more information, see Functions.
Functions are classified as either SQL functions or external functions. SQL functions are written using SQL statements, which are also known collectively as SQL procedural language. External functions reference a host language program which may or may not contain SQL statements.
A function is created with the CREATE FUNCTION statement. For more information about creating functions, see CREATE FUNCTION.
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