Order rows in a sequence and fill gaps for missing rows - tsql

Question

I got a problem regarding missing rows in a table that is giving me a headache.
As base data, I have the following table:
declare #table table
(
id1 int,
id2 int,
ch char(1) not null,
val int
)
insert into #table values (1112, 121, 'A', 12)
insert into #table values (1351, 121, 'A', 13)
insert into #table values (1411, 121, 'B', 81)
insert into #table values (1312, 7, 'C', 107)
insert into #table values (1401, 2, 'A', 107)
insert into #table values (1454, 2, 'D', 107)
insert into #table values (1257, 6, 'A', 1)
insert into #table values (1269, 6, 'B', 12)
insert into #table values (1335, 6, 'C', 12)
insert into #table values (1341, 6, 'D', 5)
insert into #table values (1380, 6, 'A', 3)
The output should be ordered by id2 and follow a fixed sequence of ch, which should repeat until next id2 begins.
Sequence:
'A'
'B'
'C'
'D'
If the sequence or the pattern is interrupted, it should fill the missing rows with null, so that i get this result table:
id1 id2 ch val
----------------------------
1112 121 'A' 12
NULL 121 'B' NULL
NULL 121 'C' NULL
NULL 121 'D' NULL
1351 121 'A' 13
1411 121 'B' 81
NULL 121 'C' NULL
NULL 121 'D' NULL
NULL 7 'A' NULL
NULL 7 'B' NULL
1312 7 'C' 107
NULL 7 'D' NULL
1401 2 'A' 107
NULL 2 'B' NULL
NULL 2 'C' NULL
1454 2 'D' 107
and so on...
What I'm looking for is a way to do this without iterations.
I hope someone can help!
Thanks in advance!

Answer 1

A solution might be this:
declare #table table ( id1 int, id2 int, ch char(1) not null, val int )
insert into #table values (1112, 121, 'A', 12)
,(1351, 121, 'A', 13),(1411, 121, 'B', 81),(1312, 7, 'C', 107),(1401, 2, 'A', 107)
,(1454, 2, 'D', 107),(1257, 6, 'A', 1),(1269, 6, 'B', 12),(1335, 6, 'C', 12)
,(1341, 6, 'D', 5),(1380, 6, 'A', 3)
;with foo as
(select
*
,row_number() over (partition by id2 order by id1) rwn
,ascii(isnull(lag(ch,1) over (partition by id2 order by id1),'A'))-ascii('A') prev
,count(*) over (partition by id2,ch) nr
,ascii(ch)-ascii('A') cur
from #table
)
,bar as
(
select
*,case when cur<=prev and rwn>1 then 4 else 0 end + cur-prev step
from foo
)
,foobar as
(
select *,sum(step) over (partition by id2 order by id1 rows unbounded preceding) rownum
from bar
)
,iterations as
(
select id2,max(nr) nr from foo
group by id2
)
,blanks as
(
select
id2,ch chnr,char(ch+ascii('A') )ch,ROW_NUMBER() over (partition by id2 order by c.nr,ch)-1 rownum,c.nr
from iterations a
inner join (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) c(nr)
on c.nr<=a.nr
cross join (values (0),(1),(2),(3)) b(ch)
)
select
b.id1,a.id2,a.ch,b.val
from blanks a
left join foobar b
on a.id2=b.id2 and a.rownum=b.rownum
order by a.id2,a.rownum
I first make the query "foo" which looks at the row number and gets the previous value for ch for each id2.
"bar" then finds how many missing values there are between the rows. For instance If the previous was an A and the current is a c then there are 2. If the previous was an A and the current is an A, then there are 4!
"foobar" then adds the steps, thus numbering the original rows, where they should be in the final output.
"iterations" counts the number of times the "ABCD" rows should appear.
"BLANKS" then is all the final rows, that is for each id2, it outputs all the "ABCD" rows that should be in the final output, and numbers them in rownum
Finally I left join "foobar" with "BLANKS" on id2 and rownum. Thus we get the correct number of rows, and the places where there are values in the original is output.

Answer 2

If you can manage to add an extra column in your table, that defines which [id2] are part from the same sequence you can try this:
declare #table table
(
id1 int,
id2 int,
ch char(1) not null,
val int,
category int -- extra column
)
insert into #table values (1112, 121, 'A', 12, 1)
insert into #table values (1351, 121, 'A', 13, 2)
insert into #table values (1411, 121, 'B', 81, 2)
insert into #table values (1312, 7, 'C', 107, 3)
insert into #table values (1401, 2, 'A', 107, 4)
insert into #table values (1454, 2, 'D', 107, 4)
insert into #table values (1257, 6, 'A', 1, 5)
insert into #table values (1269, 6, 'B', 12, 5)
insert into #table values (1335, 6, 'C', 12, 5)
insert into #table values (1341, 6, 'D', 5, 5)
insert into #table values (1380, 6, 'A', 3, 5)
DECLARE #sequence table (seq varchar(1))
INSERT INTO #sequence values ('A'), ('B'), ('C'), ('D')
SELECT b.id1, a.id2, a.seq, b.val, a.category
INTO #T1
FROM (
SELECT *
FROM #table
CROSS JOIN #sequence
) A
LEFT JOIN (
SELECT * FROM #table
) B
ON 1=1
AND a.id1 = b.id1
AND a.id2 = b.id2
AND a.seq = b.ch
AND a.val = b.val
;WITH rem_duplicates AS (
SELECT *, dup = ROW_NUMBER() OVER (PARTITION by id2, seq, category ORDER BY id1 DESC)
FROM #T1
) DELETE FROM rem_duplicates WHERE dup > 1
SELECT * FROM #T1 ORDER BY id2 DESC, category ASC, seq ASC
DROP TABLE #T1

Answer 3

I'm little confused by your output, try this:
Update
DECLARE #table TABLE
(
row INT IDENTITY(1, 1) ,
id1 INT ,
id2 INT ,
ch CHAR(1) NOT NULL ,
val INT
);
DECLARE #Sequence TABLE ( ch3 CHAR(1) NOT NULL );
INSERT INTO #Sequence
VALUES ( 'A' );
INSERT INTO #Sequence
VALUES ( 'B' );
INSERT INTO #Sequence
VALUES ( 'C' );
INSERT INTO #Sequence
VALUES ( 'D' );
INSERT INTO #table
VALUES ( 1112, 121, 'A', 12 );
INSERT INTO #table
VALUES ( 1351, 121, 'A', 13 );
INSERT INTO #table
VALUES ( 1411, 121, 'B', 81 );
INSERT INTO #table
VALUES ( 1312, 7, 'C', 107 );
INSERT INTO #table
VALUES ( 1401, 2, 'A', 107 );
INSERT INTO #table
VALUES ( 1454, 2, 'D', 107 );
INSERT INTO #table
VALUES ( 1257, 6, 'A', 1 );
INSERT INTO #table
VALUES ( 1269, 6, 'B', 12 );
INSERT INTO #table
VALUES ( 1335, 6, 'C', 12 );
INSERT INTO #table
VALUES ( 1341, 6, 'D', 5 );
INSERT INTO #table
VALUES ( 1380, 6, 'A', 3 );
SELECT r.id1 ,
fin.id2 ,
ch3 ,
r.val
FROM ( SELECT *
FROM ( SELECT CASE WHEN r.chd - l.chd = 1 THEN 0
ELSE 1
END [gap in sq] ,
l.*
FROM ( SELECT id2 ,
ASCII(ch) chd ,
ch ,
val ,
id1 ,
row
FROM #table
) AS l
LEFT JOIN ( SELECT id2 ,
ASCII(ch) chd ,
row
FROM #table
) AS r ON l.row = r.row - 1
) AS temp ,
#Sequence s
WHERE temp.[gap in sq] = 1
OR ( temp.[gap in sq] = 0
AND s.ch3 = temp.ch
)
) AS fin
LEFT JOIN #table r ON r.id2 = fin.id2
AND r.id1 = fin.id1
AND r.ch = fin.ch3