cursor loop - >while (##FETCH_STATUS=0) not going into loop - sql

Question

I have below code:
declare #prefix varchar(50)
set #prefix = 'schema1'
declare #TablesAndIdentifiers table (TableT0 varchar(50), TableX0 varchar(50), IdentifierT0 varchar(50), IdentifierX0 varchar(50))
insert into #TablesAndIdentifiers(TableT0, TableX0, IdentifierT0, IdentifierX0)
values
('table1', 'table2', 'external_Id', 'Key Details | External Id')
declare #TableT varchar(50)
declare #TableX varchar(50)
declare #IdentifierT varchar(50)
declare #IdentifierX varchar(50)
------------------------------------------OUTER LOOP------------------------------------------
declare #OuterCursor cursor
set #OuterCursor = cursor for select * from #TablesAndIdentifiers
open #OuterCursor
fetch next from #OuterCursor into #TableT, #TableX, #IdentifierT, #IdentifierX
while(##FETCH_STATUS = 0)
begin
declare #ColList2 table (ColListT varchar(50), ColListX varchar(50))
insert into #ColList2(ColListT,ColListX)
select ColListT, ColListX
from (
select COLUMN_NAME as ColListT, row_number() over (order by table_name) as r from INFORMATION_SCHEMA.Columns
where table_name = #TableT and COLUMN_NAME!=#IdentifierT) a
full outer join
(select COLUMN_NAME as ColListX, row_number() over (order by table_name) as r from INFORMATION_SCHEMA.Columns
where table_name = #TableX and COLUMN_NAME!=#IdentifierX) b
on a.r = b.r
--Declare and set variables containing the query which will insert the mismatch columns into a new table
--#sqlfull is a concatenation of #sqlpre, #sql, #sqlpost, #sqlwhere, #sqlpregroup, #sqlgroupstatement, #sqlpostgroup
--The reason for this is that #sql is the only part of the query we want to be contained in the loop - the others should run outside of the loop
declare #sqlpre varchar(max)
declare #sql varchar(max)
declare #sqlpost varchar(max)
declare #sqlgroupstatement varchar(max)
declare #sqlpostgroup varchar(max)
declare #sqlfull varchar(max)
set #sqlpre = 'select * from (select '
set #sql = ''
set #sqlpost = #IdentifierT + ' from '+#prefix+'.dbo.' +#TableX +' x inner join '+#prefix+'.dbo.' +#TableT + ' t on t.' +#IdentifierT + ' = x.[' + #IdentifierX +'])dt1 group by '
set #sqlgroupstatement = ''
set #sqlpostgroup = ' ' + #IdentifierT
declare #Cursor cursor, #ColListTvar varchar(100), #ColListXvar varchar(100)
set #Cursor = cursor for select * from #ColList2
open #Cursor
fetch next from #Cursor into #ColListTvar,#ColListXvar
Print 'Before While => ' + CAST(##FETCH_STATUS AS varchar(32))
while (##FETCH_STATUS = 0)
begin
Print 'Inside while -=> ' + CAST(##FETCH_STATUS AS varchar(32))
set #sql = #sql + 'case when t.' +#ColListTvar + ' != x.[' +#ColListXvar + '] then 1 else null end as ' + #ColListTvar+'_mismatch, '
set #sqlgroupstatement = #sqlgroupstatement + #ColListTvar+'_mismatch, '
fetch next from #Cursor into #ColListTvar,#ColListXvar
end
close #Cursor
Print 'After While => ' + CAST(##FETCH_STATUS AS varchar(32))
set #sqlfull = concat(#sqlpre,#sql,#sqlpost,#sqlgroupstatement,#sqlpostgroup)
print(#sqlfull)
--exec(#sqlfull)
declare #ColListMismatch varchar(max)
select #ColListMismatch = coalesce(#ColListMismatch+'_count,' ,'') + column_name
from INFORMATION_SCHEMA.COLUMNS where table_name = 'mismatches_' + #TableT and COLUMN_NAME!=#IdentifierT
-- The last column in the list won't get a '_count' in its name (but it needs it as the rest of the code assumes this is the naming convention)
-- See below for workaround to get round this
--Create table variable containing the list of mismatch columns (in which we want to count the non-nulls - non-null implies there has been a mismatch)
declare #ColListMismatchTable table (ColListM varchar(50))
insert into #ColListMismatchTable(ColListM)
select ColListM
from (select [COLUMN_NAME] as ColListM from INFORMATION_SCHEMA.Columns
where table_name = 'mismatches_'+#TableT and COLUMN_NAME!=#IdentifierT)dt1
--Declare variables for use in queries
declare #sqlpre2 varchar(max)
declare #sqlloop varchar(max)
declare #sqlpost2 varchar(max)
declare #sqlfull2 varchar(max)
-- Select counts from the transformation layer table and the XPLAN table; also select the count of the table produced as a result of the inner join between the two
-- If the migration has functioned correctly, these three counts should all be the same
set #sqlpre2 = 'select countXPLAN, countTransfLayer, countXPLAN-countTransfLayer as CountDiff, countMatchedIdentifiers, '
-- As mentioned above, the "+ #ColListMismatch + '_count into " part of the below is necessary to append the _count to the last variable
+ #ColListMismatch + '_count into '+#prefix+'.[dbo].report_' + #TableT + ' from '
set #sqlloop = ''
set #sqlpost2 = ' select * from ((select count(*) as countTransfLayer from '+#prefix+'.dbo.'+#TableT+')dt1 cross join (select count(*) as countXPLAN from '+#prefix+'.dbo.['+#TableX+'])dt2 cross join (select count(*) as countMatchedIdentifiers from '+#prefix+'.dbo.mismatches_'+#TableT+')dt4)'
------------------------------------------SECOND INNER LOOP------------------------------------------
--Use Cursor to create loop to produce counts for each column in mismatches_*
declare #Cursor2 cursor, #ColListMismatchvar varchar(50)
set #Cursor2 = cursor for select * from #ColListMismatchTable
open #Cursor2
fetch next from #Cursor2 into #ColListMismatchvar
while(##FETCH_STATUS = 0)
begin
-- Select all the counts of non-nulls
set #sqlloop = #sqlloop + '(select count(*) as '+ #ColListMismatchvar + '_count from mismatches_' + #TableT + ' where ' + #ColListMismatchvar + '=1)dt_' + #ColListMismatchvar + ' cross join '
fetch next from #Cursor2 into #ColListMismatchvar
end
-- Remove variables so that they can be reused by the next data entity
delete #ColListMismatchTable
select #ColListMismatch=null
close #Cursor2
print('in loop to execute sqlfull2')
set #sqlfull2 = concat(#sqlpre2,#sqlloop,#sqlpost2)
print(#sqlfull2)
-- exec(#sqlfull2)
print('executed sqlfull2')
fetch next from #OuterCursor into #TableT, #TableX, #IdentifierT, #IdentifierX
end
close #OuterCursor
out put of is:
(1 row(s) affected)
(0 row(s) affected)
Before While => -1
After While => -1
select * from (select external_Id from schema1.dbo.table22 x inner join schama1.dbo.table1 t on t.external_Id = x.[Key Details | External Id])dt1 group by external_Id
(0 row(s) affected)
(0 row(s) affected)
in loop to execute sqlfull2..
The problem i am facing code is not going into while loop of below code
declare #Cursor cursor, #ColListTvar varchar(100), #ColListXvar varchar(100)
set #Cursor = cursor for select * from #ColList2
open #Cursor
fetch next from #Cursor into #ColListTvar,#ColListXvar
Print 'Before While => ' + CAST(##FETCH_STATUS AS varchar(32))
while (##FETCH_STATUS = 0)
begin
Print 'Inside while -=> ' + CAST(##FETCH_STATUS AS varchar(32))
set #sql = #sql + 'case when t.' +#ColListTvar + ' != x.[' +#ColListXvar + '] then 1 else null end as ' + #ColListTvar+'_mismatch, '
set #sqlgroupstatement = #sqlgroupstatement + #ColListTvar+'_mismatch, '
fetch next from #Cursor into #ColListTvar,#ColListXvar
end
close #Cursor
Print 'After While => ' + CAST(##FETCH_STATUS AS varchar(32))
set #sqlfull = concat(#sqlpre,#sql,#sqlpost,#sqlgroupstatement,#sqlpostgroup)
print(#sqlfull)
--exec(#sqlfull)
any suggestions will be much appreciated.
Thanks in advance.

Answer 1

After lot of analysis i found that issue with
select ColListT, ColListX
from (
select COLUMN_NAME as ColListT, row_number() over (order by table_name) as r from INFORMATION_SCHEMA.Columns
where table_name = #TableT and COLUMN_NAME!=#IdentifierT) a
full outer join
(select COLUMN_NAME as ColListX, row_number() over (order by table_name) as r from INFORMATION_SCHEMA.Columns
where table_name = #TableX and COLUMN_NAME!=#IdentifierX) b
on a.r = b.r
Instead of Full outer join if i use inner join it worked.
There was issue with number of columns in 2 tables, one of table has less column than other, that's the reason it wasn't working properly.