Pl/Sql using instr to find exact match - string

Question

I am trying to find if a string exist in a word and extract it. I have uses the instr() function but this works as the LIKE function: if part or the whole word exists it returns it.
Here I want to get the string 'Services' out, it works but if I change 'Services' to 'Service' it still works. I don't want that. If 'Service' is entered it should return null and not 'Services'
Modified:
What I am trying to do here is abbreviate certain parts of the company name.
This is what my database table looks like :
Word | Abb
---------+-----
Company | com
Limited | ltd
Service | serv
Services | servs
Here is the code:
Declare
Cursor Words Is
SELECT word,abb
FROM abbWords
processingWord VARCHAR2(50);
abbreviatedName VARCHAR(120);
fullName = 'A.D Company Services Limited';
BEGIN
FOR eachWord IN Words LOOP
--find the position of the word in name
wordPosition := INSTR(fullName, eachWord.word);
--extracts the word form the full name that matches the database
processingWord := Substr(fullName,instr(fullName,eachWord.word), length(eachWord.word));
--only process words that exist in name
if wordPosition > 0 then
abbreviatedName = replace(fullName, eachWord.word,eachWord.abb);
end if;
END lOOP;
END;
So if the user enters 'Service' I don't want 'Services' to be returned. By this I mean word position should be 0 if the word 'Service' in not found instead of returning the position for the word 'Services'

Answer 1

One way of doing it:
DECODE(INSTR('A.D Company Seervices Limited','Services'),
0,
NULL,
SUBSTR('A.D Company Services Limited',
INSTR('A.D Company Services Limited','Services'),
length('Services')))
INSTR() will return 0 if text is not found. DECODE() will evaluate the first argument, compare to the second, if match, return third argument, if not, return fourth argument. (sqlfiddle link)
Arguably not the most elegant way, but matches your requirement.

Answer 2

I think you're over-complicating this. You can do everything with regular expressions. For instance; given the following table:
create table names ( name varchar2(100));
insert into names values ('A.D Company Services Limited');
insert into names values ('A.D Company Service Limited');
This query will only return the name 'A.D Company Services Limited'.
select *
from names
where regexp_like( name
, '(^|[[:space:]])services($|[[:space:]])'
, 'i' )
This means match the beginning of the string, ^, or a space followed by services followed the end of the string, $, or a space. This is what differentiates regular expressions from using instr etc. You can make your matches easily conditional on other factors.
However, though this seems to be your question I don't think this is what you're trying to do. You're trying to replace the string 'serv' in your wider string without replacing 'services' or 'service'. For this you need to use regexp_replace().
If I add the following row to the table:
insert into names values ('A.D Company Serv Limited');
and run this query:
select regexp_replace( name
, '(^|[[:space:]])serv($|[[:space:]])'
, ' Services '
, 1, 0, 'i' )
from names
The only thing that will change is ' Serv ', which in this newest line, will be replaced with ' Services '. Note the spaces; as you don't want to replace 'Services' with 'ServServices' these are very important.
Here's a little SQL Fiddle to demonstrate.

Answer 3

Another alternative is to use something like:
select replace(name,' serv ', ' Services ')
from names;
This will replace only the word 'Serv' situated between 2 spaces.
Thank you,
Alex.

Answer 4

INSTR returns a number: the index of the first occurrence of the matching string. You should use regexp_substr instead (10g+):
SQL> select regexp_substr('A.D Company Services Limited', 'Services') match,
2 regexp_substr('A.D Company Service Limited', 'Services') unmatch
3 from dual;
MATCH UNMATCH
-------- -------
Services