如何选择一个没有前n个字符和后m个字符的字段？

Question

I have a SELECT statement that is trying to view data from a single table. The data is encapsulated by HTML tags ( <p> and </p> ). For instance, one field might say:

<p>Lorem Ipsum</p>

How do I tell the SELECT statement to discount the first 3 characters and the last 4 characters?

Answer 1

SELECT SUBSTRING(data, 4, LENGTH(data)-7)

Answer 2

If all data has only one opening tag at the beginning, and one closing tag at the end, like in your example, you could use this:

select
  case when instr(data, '</')>instr(data, '>') then
    substring(data, instr(data, '>')+1,instr(data, '</')-instr(data, '>')-1)
  else
    data
  end as stripped_data
from
  your_table

notice that this will strip also unmatched tags like <p>Lorem Ipsum</strong>