Merge two field into One with only new items

Question

I have two tables which both contain 'pipe separated values'

e.g:

Table 1:

 DataField_A

 item 1|item 2|item 3|etc.....

Table 2:

 DataField_A

 item 7|item 5|item 3|etc.....

I need to merge Table 2 into table 1 such that Table 2 contains all items across both tables.

Doing this pro-grammatically would be a simple matter of looping through each item in table 2 and adding to table 1 if it does not exist in table 1.

How can this be done in SQL as a stored procedure?

Answer 1

I've used a parsing function (the example I'm using comes from here) to parse the string in Table1. Then I use that function in a CTE to find missing elements in Table2 and merge the data.

/* Helper function to parse delimited string */
CREATE FUNCTION [dbo].[fnParseStringTSQL] (@string NVARCHAR(MAX),@separator NCHAR(1))
RETURNS @parsedString TABLE (string NVARCHAR(MAX))
AS 
BEGIN
   DECLARE @position int
   SET @position = 1
   SET @string = @string + @separator
   WHILE charindex(@separator,@string,@position) <> 0
      BEGIN
         INSERT into @parsedString
         SELECT substring(@string, @position, charindex(@separator,@string,@position) - @position)
         SET @position = charindex(@separator,@string,@position) + 1
      END
     RETURN
END
go

/* Set up some sample data */
declare @Table1 table (
    id int,
    DataField_1A varchar(500)
)

declare @Table2 table (
    id int,
    DataField_2A varchar(500)
)

insert into @Table1
    (id, DataField_1A)
    select 1, 'item 1|item 2|item 3'
    union
    select 2, 'item A|item B|item C|item D|item Z'

insert into @Table2
    (id, DataField_2A)
    select 1, 'item 7|item 5|item 3'
    union
    select 2, 'item A|item Y|item Z'

/* data before the update */
select * from @Table2

/* boolean to ensure loop executes at least once */
declare @FirstLoop bit
set @FirstLoop = 1

/* Do the updates */
while (@FirstLoop = 1 or @@ROWCOUNT <> 0) begin 
    set @FirstLoop = 0

    ;with cteMissingItems as (
    select t2.id, p.string
        from @Table2 t2
            inner join @Table1 t1
                on t2.id = t1.id
            cross apply dbo.fnParseStringTSQL(t1.DataField_1A,'|') p
        where charindex(p.string, t2.DataField_2A) = 0
    )
    update t2
        set t2.DataField_2A = t2.DataField_2A + '|' + mi.string
        from @Table2 t2
            inner join cteMissingItems mi
                on t2.id = mi.id
end /* while */

/* Prove the update worked */
select * from @Table2

/* Clean up */
drop function dbo.fnParseStringTSQL