Question

How do I get the nth word in a sentence or a set of strings with space delimiter?

Sorry for the change in the requirement.Thank you.

Answer 1

By using instr.

select substr(help, 1, instr(help,' ') - 1)
  from ( select 'hello my name is...' as help
           from dual )

instr(help,' ') returns the positional index of the first occurrence of the second argument in the first, inclusive of the string you’re searching for. i.e. the first occurrence of ' ' in the string 'hello my name is...' plus the space.

substr(help, 1, instr(help,' ') - 1) then takes the input string from the first character to the index indicated in instr(.... I then remove one so that the space isn’t included..

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For the nth occurrence just change this slightly:

instr(help,' ',1,n) is the nth occurrence of ' ' from the first character. You then need to find the positional index of the next index instr(help,' ',1,n + 1), lastly work out the difference between them so you know how far to go in your substr(.... As you’re looking for the nth, when n is 1 this breaks down and you have to deal with it, like so:

select substr( help
             , decode( n
                     , 1, 1
                     , instr(help, ' ', 1, n - 1) + 1
                       )
             , decode( &1
                     , 1, instr(help, ' ', 1, n ) - 1
                     , instr(help, ' ', 1, n) - instr(help, ' ', 1, n - 1) - 1
                       )
               )
  from ( select 'hello my name is...' as help
           from dual )

This will also break down at n. As you can see this is getting ridiculous so you might want to consider using regular expressions

select regexp_substr(help, '[^[:space:]]+', 1, n )
  from ( select 'hello my name is...' as help
           from dual )