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 结果是 te select substr('emros',-3,1) value from dual 结果是 r substr('abcde',-6) = null substr('abcde',-5) = 'abcde' substr('abcde',-4) = 'bcde' substr('abcde',-3) = 'cde' substr('abcde',-2) = 'de' substr('abcde',-1) = 'e' substr('abcde',-0) = 'abcde'