This is how my table(Table1) is currently in Oracle database.
ID Year_Mth Product
123 201901 1,2,3
123 201902 1,2,4,5
123 201903 2,3,4,6
123 201904 1,4,5,6
I am trying to get an output that compares Product column for every row to get something like below: Here, I am comparing Row 1 with Row 2 to see if Row 2 has New Products (NEW_PRODUCTS) that were not there in Row 1.
It seems that I can either use LAG, or LEAD function but it seems tricky because of ,
delimiters between products.
ID Year_Mth Product New_Products
123 201901 1,2,3 1,2,3
123 201902 1,2,4,5 4,5
123 201903 2,3,4,6 3,6
123 201904 1,4,5,6 1,5
Here's one option. Looks as ugly as your data model:) See comments within code. If you're unsure of what each CTE does, I suggest you run the following code step-by-step and review its results.
For readability, I'll split it to several parts.
SQL> with
2 test (id, year_mth, product) as
3 -- your sample data (as well as some of my sample data)
4 (select 123, 201901, '1,2,3' from dual union all
5 select 123, 201902, '1,2,4,5' from dual union all
6 select 123, 201903, '2,3,4,6' from dual union all
7 select 123, 201904, '1,4,5,6' from dual union all
8 --
9 select 888, 201901, 'apple,banana' from dual union all
10 select 888, 201902, 'apple,banana' from dual union all
11 select 888, 201903, 'apple,lemon' from dual
12 ),
13 py as
14 (select id,
15 year_mth ymp, -- "this" year_mth
16 lead(year_mth) over (partition by id order by year_mth) ymn -- "next" year_mth
17 from test
18 order by id, year_mth
19 ),
20 tabp as
21 -- products that belong to "THIS" year_mth split to rows
22 (select
23 t.id,
24 t.year_mth,
25 p.ymp,
26 p.ymn,
27 regexp_substr(t.product, '[^,]+', 1, c.column_value) product
28 from test t join py p on t.id = p.id and t.year_mth = p.ymp cross join
29 table(cast(multiset(select level from dual
30 connect by level <= regexp_count(product, ',') + 1
31 ) as sys.odcinumberlist)) c
32 ),
33 tabn as
34 -- products that belong to "NEXT" year_mth split to rows
35 (select
36 t.id,
37 t.year_mth,
38 p.ymp,
39 p.ymn,
40 regexp_substr(t.product, '[^,]+', 1, c.column_value) product
41 from test t join py p on t.id = p.id and t.year_mth = p.ymn cross join
42 table(cast(multiset(select level from dual
43 connect by level <= regexp_count(product, ',') + 1
44 ) as sys.odcinumberlist)) c
45 ),
46 newprod as 47 -- MINUS set operator finds differences between "NEXT" and "THIS" year_mth 48 (select id, ymn, product from tabn 49 minus 50 select id, ymn, product from tabp 51 ) 52 -- finally, aggregate new products (result of the previous MINUS set operation) 53 select 54 t.id, 55 t.year_mth, 56 t.product, 57 listagg(case when t.rn = 1 then t.product else n.product end, ',') 58 within group (order by n.product) new_products 59 from (select a.id, 60 a.year_mth, 61 a.product, 62 row_number() over (partition by a.id order by a.year_mth) rn 63 from test a 64 ) t left join newprod n on t.id = n.id and t.year_mth = n.ymn 65 group by t.id, t.year_mth, t.product 66 order by t.id, t.year_mth;
ID YEAR_MTH PRODUCT NEW_PRODUCTS
123 201901 1,2,3 1,2,3 123 201902 1,2,4,5 4,5 123 201903 2,3,4,6 3,6 123 201904 1,4,5,6 1,5 888 201901 apple,banana apple,banana 888 201902 apple,banana 888 201903 apple,lemon lemon
7 rows selected.
SQL>
In cases when you need to work with such delimited strings, it's often very convenient to use xml-functions, such as fn:string-join(), fn:tokenize().
For example:
xmltable(
'let $x:=tokenize($a,","), $y:=tokenize($b,",")
return fn:string-join($x[not(.=$y)],",")'
passing product as "a"
,prev_product as "b"
columns New_Products varchar(100) path '.'
) x
This xmltable() splits input parameters product and prev_product and returns those substrings from product that are not in prev_product:
tokenize($a, ",")
splits input string $a using comma as a delimiter. $x[not(.=$y)]
returns those values from $x that do not exist in $y string-join($arg1, ",")
concatenates values from $arg1 using comma as a delimiter. Full example:
with
test (id, year_mth, product) as
-- your sample data (as well as some of my sample data)
(select 123, 201901, '1,2,3' from dual union all
select 123, 201902, '1,2,4,5' from dual union all
select 123, 201903, '2,3,4,6' from dual union all
select 123, 201904, '1,4,5,6' from dual union all
--
select 888, 201901, 'apple,banana' from dual union all
select 888, 201902, 'apple,banana' from dual union all
select 888, 201903, 'apple,lemon' from dual
)
select
t.*
,x.*
from
(
select
t.*
,lag(t.product)over(partition by id order by year_mth) prev_product
from test t
) t
,xmltable(
'let $x:=tokenize($a,","), $y:=tokenize($b,",")
return fn:string-join($x[not(.=$y)],",")'
passing product as "a"
,prev_product as "b"
columns New_Products varchar(100) path '.'
) x;
I made the xquery above so long just to make it more readable. In real life xquery would be much shorter: fn:string-join(tokenize($a,",")[not(.=tokenize($b,","))],",")
with
test (id, year_mth, product) as
-- your sample data (as well as some of my sample data)
(select 123, 201901, '1,2,3' from dual union all
select 123, 201902, '1,2,4,5' from dual union all
select 123, 201903, '2,3,4,6' from dual union all
select 123, 201904, '1,4,5,6' from dual union all
--
select 888, 201901, 'apple,banana' from dual union all
select 888, 201902, 'apple,banana' from dual union all
select 888, 201903, 'apple,lemon' from dual
)
select
t.*
,x.*
from
(
select
t.*
,lag(t.product)over(partition by id order by year_mth) prev_product
from test t
) t
,xmltable(
'fn:string-join(tokenize($a,",")[not(.=tokenize($b,","))],",")'
passing product as "a"
,prev_product as "b"
columns New_Products varchar(100) path '.'
) x
Mine is similar, add a listagg and group-by query at the end if you want to re-pivot...
WITH
input(id,year_mth,product) AS (
SELECT 123,201901,'1,2,3' FROM dual
UNION ALL SELECT 123,201902,'1,2,4,5' FROM dual
UNION ALL SELECT 123,201903,'2,3,4,6' FROM dual
UNION ALL SELECT 123,201904,'1,4,5,6' FROM dual
)
,
i(i) AS (
SELECT 1 FROM dual
UNION ALL SELECT 2 FROM dual
UNION ALL SELECT 3 FROM dual
UNION ALL SELECT 4 FROM dual
UNION ALL SELECT 5 FROM dual
)
,
unpivot AS (
SELECT
id
, i
, year_mth
, REGEXP_SUBSTR(product,'\d+',1,i) AS prd
FROM input CROSS JOIN i
WHERE REGEXP_SUBSTR(product,'\d+',1,i) <> ''
)
SELECT
*
, CASE
WHEN LAG(year_mth) OVER(PARTITION BY id,prd ORDER BY year_mth) IS NULL
THEN 'new'
ELSE 'old'
END
FROM unpivot ORDER BY 3,4;
-- out id | i | year_mth | prd | case
-- out -----+---+----------+-----+------
-- out 123 | 1 | 201901 | 1 | new
-- out 123 | 2 | 201901 | 2 | new
-- out 123 | 3 | 201901 | 3 | new
-- out 123 | 1 | 201902 | 1 | old
-- out 123 | 2 | 201902 | 2 | old
-- out 123 | 3 | 201902 | 4 | new
-- out 123 | 4 | 201902 | 5 | new
-- out 123 | 1 | 201903 | 2 | old
-- out 123 | 2 | 201903 | 3 | old
-- out 123 | 3 | 201903 | 4 | old
-- out 123 | 4 | 201903 | 6 | new
-- out 123 | 1 | 201904 | 1 | old
-- out 123 | 2 | 201904 | 4 | old
-- out 123 | 3 | 201904 | 5 | old
-- out 123 | 4 | 201904 | 6 | old
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