oracle的substr函数的用法 取得字符串中指定起始位置和长度的字符串 substr( string, start_position, [ length ] ) 如: substr(‘This is a test‘, 6, 2) would return‘is‘ substr(‘This is a test‘, 6) would return‘is a test‘ substr(‘TechOnTheNet‘, -3, 3) would return‘Net‘ substr(‘TechOnTheNet‘, -6, 3) would return‘The‘
select substr(‘Thisisatest‘, -4, 2) value from dual