oracle中substr oracle中substr函数的用法

oracle中substr函数的用法  

　　In oracle/PLSQL the substr functions allows you to extract a substring from a string

　　The syntax for the substr function is:

　　substr( string start_position [ length ] )

　　说明

　　string is the source string

　　start_position is the position for extraction The first position in the string is always

　　length is optional It is the number of characters to extract If this parameter is omitted substr will return the entire string

　　For example:

　　substr( This is a test ) would return is

　　substr( This is a test ) would return is a test

　　substr( TechOnTheNet ) would return Tech

　　substr( TechOnTheNet ) would return Net

　　substr( TechOnTheNet ) would return The