Oracle replacing text between first and last spaces - sql

Question

Here is the table data with the column name as Ships.
+--------------+
Ships |
+--------------+
Duke of north |
---------------+
Prince of Wales|
---------------+
Baltic |
---------------+
Replace all characters between the first and the last spaces (excluding these spaces) by symbols
of an asterisk (*). The number of asterisks must be equal to number of replaced characters.

Answer 1

Regular expressions are your friend :)
First match the space, followed by any other characters, ending in a space.
Then replace that with a string that consists of the starting and trailing space and, in between, a string of asterisks.
The string of asterisks is made by right padding a single asterisk with further asterisks to the appropriate length. That length is the length of the regular expression matched minus two characters for the leading/trailing space.
select regexp_replace(column_value,' .* ',
' '||rpad('*',length(regexp_substr(column_value,' .* '))-2,'*')||' ')
from table(sys.dbms_debug_vc2coll(
'Duke of north','Prince of Wales','Baltic','what if two spaces'));
Duke ** north
Prince ** Wales
Baltic
what ****** spaces

Answer 2

This really smells like homework. So I won't provide you with the full deal, but point you in the right direction instead:
Check out the function InStr. Espcecially its 3rd and 4th parameters, that allow you to search starting at the Xth char and/or search the Yth occurrence.
Edit: If someone finds this thread in a search and hopes for a solution that works in older versions of Oracle, this is how I'd have done it.
(I posted it as a comment to another post, but the author deleted his answer for some inexplicable reason o_O )
SELECT case
when InStr(Name, ' ', 1) > 0 and
InStr(Name, ' ', 1) <> InStr(Name, ' ', -1) then
SubStr(Name, 1, InStr(Name, ' ', 1) - 1) ||
lPad('*', InStr(Name, ' ', -1) - InStr(Name, ' ', 1) + 1, '*') ||
SubStr(Name, InStr(Name, ' ', -1) + 1)
else
Trim(Name)
end
FROM SomeTable

Answer 3

Although the data in the original question only had one word in between, it is possible to have more than one word in between the first and the last the word. For example:"This is an example with more than one word"
I suppose the solution should be such that it handles all these as well....
Anyway, here is another solution:
With
I As(
/*Serves as an input parameter*/
Select 'This is an example with more than one word' Str From Dual
)
,D As(
/*Split words into rows*/
Select RegExp_SubStr(Str,'[^ ]+',1,Level) Word,RowNum Seq,First_value(RowNum) Over(Order By RowNum Desc) L
From I
Connect By RegExp_SubStr(Str,'[^ ]+',1,Level) Is Not NULL
)
Select
/*Assemble all together - other than the first and the last word, replace all the rest into "*"*/
--uncomment the ListAgg statement if using 11g--
--ListAgg(Decode(Seq,1,Word,L,Word,RegExp_Replace(Word,'.','*')),' ') Within Group(Order By Seq) Statement
--If using earlier version of Oracle then use the following--
Trim(RegExp_Replace(XMLAgg(XMLElement(R,Decode(Seq,1,Word,L,Word,RegExp_Replace(Word,'.','*'))||' ') Order By Seq),'</?R>')) Statement
From D
/
OUTPUT:
This ** ** ******* **** **** **** *** word

Answer 4

SELECT a actual_string,
first_word,
SUBSTR(output1,1,LENGTH(output1)-LENGTH(SUBSTR(output1,(
CASE
WHEN regexp_count(output1,' ')=0
THEN 0
ELSE regexp_instr(output1,' ',1,regexp_count(output1,' '))
END)+1))) middle_words,
last_word,
CASE
WHEN first_word=last_word
THEN first_word
ELSE first_word
||TRANSLATE(upper(SUBSTR(output1,1,LENGTH(output1)-LENGTH(SUBSTR(output1,(
CASE
WHEN regexp_count(output1,' ')=0
THEN 0
ELSE regexp_instr(output1,' ',1,regexp_count(output1,' '))
END)+1)))),'ABCDEFGHIJKLMNOPQRSTUVWXYZ','**************************')
||last_word
END final_result
FROM
(SELECT a,
CASE
WHEN SUBSTR(a,1,regexp_instr(a,' ',1)) IS NULL
THEN a
ELSE SUBSTR(a,1,regexp_instr(a,' ',1))
END first_word,
SUBSTR(a,(
CASE
WHEN regexp_count(a,' ')=0
THEN 0
ELSE regexp_instr(a,' ',1,regexp_count(a,' '))
END)+1) last_word,
SUBSTR(a, LENGTH(
CASE
WHEN SUBSTR(a,1,regexp_instr(a,' ',1)) IS NULL
THEN a
ELSE SUBSTR(a,1,regexp_instr(a,' ',1))
END)+1, LENGTH(SUBSTR(a,(
CASE
WHEN regexp_count(a,' ')=0
THEN 0
ELSE regexp_instr(a,' ',1,regexp_count(a,' '))
END)+1))-2) middle_words,
CASE
WHEN regexp_instr(a,' ',1) +1>1
THEN SUBSTR(a,regexp_instr(a,' ',1)+1,
CASE
WHEN regexp_count(a,' ')=0
THEN 0
ELSE regexp_instr(a,' ',1,regexp_count(a,' '))
END )
ELSE a
END output1--,
FROM
( SELECT 'Duke of north' a FROM dual
UNION
SELECT 'Prince of Wales' a FROM dual
UNION
SELECT 'Baltic' a FROM dual
UNION
SELECT 'what if two spaces' a FROM dual
UNION
SELECT 'what if two or spaces' a FROM dual
)
)