Filter those data from table where there is a gap in sequence

问题

I want to set the doprocess flag to 0 if the below data is empty between any of the targets mentioned

Example:

create table TestSAMP (
  id int identity(1,1),
  modelid navrchar(max),
  target1 nvarchar(max),
  target2 nvarchar(max),
  target3 nvarchar(max),
  target4 nvarchar(max),
  doprcoess  int default(1)
)

--VALID SET DOPROCESS FLAG TO 1
INSERT INTO TestSAMP(modelid,target1,target2,target3,target4) 
VALUES('1','T1','T2','T3','T4')

--NOTVALID SET DOPROCESS FLAG TO 0 DUE TO THE DATA IS MISSING IN SEQUENCE 
INSERT INTO TestSAMP(modelid,target1,target2,target3,target4)
VALUES('2','TR','','T3','T4')

--VALID SET DOPROCESS FLAG TO 1 As if data is present
-- it should be present insequence in below t1 t2 as they arfe in sequence
INSERT INTO TestSAMP(modelid,target1,target2,target3,target4)
VALUES('3','T1','T2','','')

--NOTVALID SET DOPROCESS FLAG TO 0 DUE TO THE DATA IS MISSING IN SEQUENCE 
--where T4 data is provided and not in T3
INSERT INTO TestSAMP(modelid,target1,target2,target3,target4) 
VALUES('4','T1','T2','','T4')

I have got lot of solution where people try out to find the sequential number but here the case is nvarchar

回答1:

You could treat gaps and islands as string i.e. 'IGGI', squash it, and search for 'IGI' pattern:

SELECT *, CASE WHEN squashed LIKE '%IGI%' THEN 0 ELSE 1 END AS new_doprocess
FROM TestSAMP t
CROSS APPLY(SELECT STRING_AGG(CASE WHEN t = '' THEN 'G' ELSE 'I'END, '') r
             FROM (VALUES (1,id, target1), (2,id, target2),
                          (3,id, target3), (4,id, target4)) sub(rn, id, t)) s
CROSS APPLY (SELECT replace(replace(replace(replace(replace(replace(s.r,'G','<>')
   ,'><',''),'<>','G'),'I','<>'),'><',''),'<>','I')) AS sub(squashed)
ORDER BY t.id;

db<>fiddle demo

Example:

  id  | target1  | target2  | target3  | target4  |  r    | squashed  | doprocess 
 -----|----------|----------|----------|----------|-------|-----------|----------- 
   1  | T1       | T2       | T3       | T4       | IIII  | I         |         1 
   2  | T1       |          | T3       | T4       | IGII  | IGI       |         0 
   3  | T1       | T2       |          |          | IIGG  | IG        |         1 
   4  | T1       | T2       |          | T4       | IIGI  | IGI       |         0 
   5  |          |          |          | T4       | GGGI  | GI        |         1 
   6  |          |          |          |          | GGGG  | G         |         1

回答2:

The easiest way should be a Boolean expression checking if a predecessor is empty when a successor is not.

UPDATE testsamp
       SET doprocess = 0
       WHERE target2 <> ''
             AND target1 = ''
              OR target3 <> ''
                 AND target2 = ''
               OR target4 <> ''
                   AND target3 = '';

You might want to extend it for example if it's also invalid, when all targets are empty. I don't know if you want that.

来源：https://stackoverflow.com/questions/53923146/filter-those-data-from-table-where-there-is-a-gap-in-sequence

标签

sql

sql-server

tsql

gaps-and-islands