SQL Server finds the position of the nth occurrence of a character in a string

Source: Internet
Author: User

前几天的考试系统出现了一个问题,背景大概就是告诉你正确答案,比如说是:答案1#答案2#答案3...而几百个学生答题的记录也是这样格式存储的,问如何用sql语句为每个学生判分?
思路:
第一步:找到第N个#在字符串中的位置
create
  function  fn_find(@find  varchar (8000), @str  varchar (8000), @n  smallint )      returns  int as begin      if @n < 1  return  (0)      declare  @start  smallint , @ count  smallint , @ index  smallint , @len  smallint      set  @ index  = charindex(@find, @str)      if @ index  = 0  return  (0)      else  select  @ count  = 1, @len = len(@find)      while @ index  > 0  and  @ count  < @n          begin              set  @start = @ index  + @len              select  @ index  = charindex(@find, @str, @start), @ count  = @ count  + 1          end      if @ count  < @n  set  @ index  = 0      return  (@ index ) end go
第二步:
截取学生第N道题的答案和正确答案第N道题做比较,把做对的人的分数加1。
update dbo.T_dxyysyj_BankedCloze2_Record
set Fraction =Fraction +1
where QuestionID =‘3‘ and SUBSTRING(ExamAnswer,dbo.fn_find(@find,@str,@mystart)+1,@mylength)=SUBSTRING(@str,dbo.fn_find(@find,@str,@mystart)+1,@mylength)
第三步:
封装成存储过程。

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SQL Server finds the position of the nth occurrence of a character in a string

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