oracle笔记（2）----substr使用

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"