SQL Server 2019

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CREATE TABLE [dbo].[TABLEA](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [DocNumber] [varchar](50) NULL,
    [InternalDocNumber] [varchar](50) NULL,
    [Date] [varchar](50) NULL,
    [DocType] [varchar](50) NULL,
    [Description] [varchar](50) NULL,
    [NameG] [varchar](max) NULL,
    [NameGR] [varchar](max) NULL,
    [NumberPages] [varchar](50) NULL)
INSERT INTO [dbo].[TABLEA]
           ([DocNumber]
           ,[InternalDocNumber]
           ,[Date]
           ,[DocType]
           ,[Description]
           ,[NameG]
           ,[NameGR]
           ,[NumberPages])
     VALUES
           (1
           ,1235
           ,'12/23/2020'
           ,3
           ,'this is a test'
           ,'test1, test2, test3'
           ,'test6, test4'
           ,1),
           (2
           ,3456
           ,'12/24/2020'
           ,3
           ,'this is a test1'
           ,'test4, test5, test6'
           ,'test9, test4'
           ,2)
           ,
           (6
           ,6789
           ,'12/24/2020'
           ,3
           ,'this is a test3'
           ,'test9'
           ,'test100, test15, test16'
           ,2)
3 rows affected

with cte as (
      select a.docnumber, convert(varchar(max), null) as gr, convert(varchar(max), null) as g,
             convert(varchar(max), nameGR) as restGR, convert(varchar(max), nameG) as restG, 0 as lev
      from tableA a
      union all
      select cte.docnumber,
             left(restgr, charindex(',', restgr + ',') - 1) as gr,
             left(restg, charindex(',', restg + ',') - 1) as g,
             stuff(restgr, 1, charindex(',', restgr + ',') + 1, '') as restgr,
             stuff(restg, 1, charindex(',', restg + ',') + 1, '') as restg,
             lev + 1
      from cte
      where (restgr > '' or restg > '') and lev < 10
     )
select docnumber, gr, g
from cte
where lev > 0


docnumber
gr
g


6
test100
test9

6
test15


6
test16
null

2
test9
test4

2
test4
test5

2

test6

1
test6
test1

1
test4
test2

1

test3
docnumber	gr	g
6	test100	test9
6	test15
6	test16	null
2	test9	test4
2	test4	test5
2		test6
1	test6	test1
1	test4	test2
1		test3