楼主，你自己有尝试看帮助文件？
  strpos(s1,s2)
       Domain s1:    strings (to be searched)
       Domain s2:    strings (to search for)
       Range:        integers 0 to 244
       Description:  returns the position in s1 at which s2 is first found; otherwise, it returns 0.
                         strpos("this","is") = 3
                         strpos("this","it") = 0


substr(s,n1,n2)
       Domain s:     strings
       Domain n1:    integers 1 to 244 and -1 to -244
       Domain n2:    integers 1 to 244 and -1 to -244
       Range:        strings
       Description:  returns the substring of s, starting at column n1, for a length of n2. If n1 < 0, n1 is interpreted as distance from the end of the string; if
                         n2 = . (missing), the remaining portion of the string is returned.

                         substr("abcdef",2,3) = "bcd"

还是不太懂！不过还是要谢谢您的回答！

不要看陈传波的
要是看的话,必定走弯路