How to compare 2 columns and return the difference in oracle SQL - oracle

Question

We have 2 columns in one table in oracle SQL as
Col1= "there is book on the table"
Col2= "there are flowers on the chair"
Now I need the result as differed data in the column3 as new column col3.
The col3 result should be
"are flowers chair".
How to achieve this in oracle SQL??

Answer 1

You can use:
WITH words ( rid, col, name, id, word ) AS (
SELECT rid,
CASE INSTR(col, ' ')
WHEN 0
THEN NULL
ELSE SUBSTR(col, INSTR(col, ' ') + 1)
END,
name,
1,
CASE INSTR(col, ' ')
WHEN 0
THEN col
ELSE SUBSTR(col, 1, INSTR(col, ' ') - 1)
END
FROM ( SELECT ROWID AS rid, col1, col2 FROM table_name )
UNPIVOT ( col FOR name IN (col1, col2) )
UNION ALL
SELECT rid,
CASE INSTR(col, ' ')
WHEN 0
THEN NULL
ELSE SUBSTR(col, INSTR(col, ' ') + 1)
END,
name,
id + 1,
CASE INSTR(col, ' ')
WHEN 0
THEN col
ELSE SUBSTR(col, 1, INSTR(col, ' ') - 1)
END
FROM words
WHERE col IS NOT NULL
),
paired_words ( rid, id1, id2 ) AS (
SELECT c1.rid,
c1.id AS id1,
c2.id AS id2
FROM ( SELECT rid, id, word FROM words WHERE name = 'COL1' ) c1
INNER JOIN
( SELECT rid, id, word FROM words WHERE name = 'COL2' ) c2
ON (c1.rid = c2.rid AND c1.word = c2.word)
),
max_path ( rid, path ) AS (
SELECT rid,
path
FROM (
SELECT rid,
SYS_CONNECT_BY_PATH(id2, ',') || ',' AS path,
ROW_NUMBER() OVER (PARTITION BY rid ORDER BY LEVEL DESC) AS rn
FROM paired_words
CONNECT BY PRIOR rid = rid
AND PRIOR id1 < id1
AND PRIOR id2 < id2
)
WHERE rn = 1
)
SELECT LISTAGG(word, ' ') WITHIN GROUP (ORDER BY id) AS missing
FROM words w
WHERE NOT EXISTS (
SELECT 1
FROM max_path mp
WHERE w.rid = mp.rid
AND mp.path LIKE '%,' || w.id || ',%'
)
AND w.name = 'COL2'
GROUP BY rid;
Which, for the sample data:
CREATE TABLE table_name ( col1, col2 ) AS
SELECT 'there is book on the table', 'there are flowers on the chair' FROM DUAL UNION ALL
SELECT 'there is book on the table', 'there is a book on the table' FROM DUAL UNION ALL
SELECT 'there is book on the table', 'there is book there is book on the table on the table' FROM DUAL
Outputs:
MISSING
are flowers chair
a
there is book on the table
db<>fiddle here

Answer 2

Here's one option (which follows what you asked). Read comments within code.
SQL> with test (id, col1, col2) as
2 (select 1, 'there is book on the table',
3 'there are flowers on the chair'
4 from dual
5 ),
6 -- split sentences into words (each in its own line)
7 sent1 as
8 (select id,
9 column_value cv,
10 regexp_substr(col1, '[^ ]+', 1, column_value) word
11 from test cross join
12 table(cast(multiset(select level from dual
13 connect by level <= regexp_count(col1, ' ') + 1
14 ) as sys.odcinumberlist))
15 ),
16 sent2 as
17 (select id,
18 column_value cv,
19 regexp_substr(col2, '[^ ]+', 1, column_value) word
20 from test cross join
21 table(cast(multiset(select level from dual
22 connect by level <= regexp_count(col2, ' ') + 1
23 ) as sys.odcinumberlist))
24 )
25 -- final result
26 select a.id,
27 listagg(b.word, ' ') within group (order by a.cv) result
28 from sent2 b join sent1 a on a.id = b.id and a.cv = b.cv and a.word <> b.word
29 group by a.id;
ID RESULT
---------- ------------------------------
1 are flowers chair
SQL>