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Select the next available record in a SQL table based on last record in another table

Posted on 2014-11-10
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Last Modified: 2014-11-12
Hello Experts,

I have two SQL Tables that look like this:

Tbl 1:

Type    Wt
1           10.0
2           10.2
3           11.3

Tbl 2:

Type    Wt
1           10.0
2           10.2
3           11.3
7           22.5

I want to add new records in Tbl 2 to Tbl1 based on the last record in Tbl1.

The following code works fine as long as "Type" values are sequential in Tbl2.

@LastTypPlusOne = Select MAX(Type) From Tb_1

Insert Into Tbl1(Type, Wt)
Select Type, Wt
From Tbl2
Where Type = @LastTypPlusOne + 1

(The record with a "Type" value of 7 will not Insert...)

-- The last Type value in Tbl1 is 3
-- There is no Type value 4, 5 or 6 in Tbl2
-- The next new record (has Type value of 7) in Tbl2 needs to be inserted into Tbl1 based on last Type value in Tbl1.

I would like to Insert all new records from Tbl2 into Tbl1 based on the  "Type" value in the last record in Tbl1.

Does anyone know how to do this??

Thanks!
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Question by:Saxitalis
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6 Comments
 
LVL 34

Expert Comment

by:Mike Eghtebas
ID: 40434153
Would try this. This is done in SQL Server Express 2012; please make necessary adjustment if SS2005 different:
declare @LastTbl_1 int;
declare @NextTbl_2 int;
declare @MaxTbl_2 int;
declare @ExistsInTbl_2 int;
select @LastTbl_1 = max(Type) From Tbl_1;
select @MaxTbl_2 = max(Type) From Tbl_2;  -- used later to end the loop

set @LastTbl_1 =  @LastTbl_1 + 1;

While(@ExistsInTbl_2= 0) 
begin

  select @NextTbl_2 = Type From Tbl_2 Where Type = @LastTbl_1;

  if @NextTbl_2>0 
  begin  -- match is found

     Set @ExistsInTbl_2 = 1; -- to get out of the loop

	 Insert Into Tbl_1(Type, Wt)
      Select Type, Wt
      From Tbl_2
      Where Type = @NextTbl_2;

  end

	if @MaxTbl_2= @LastTbl_1
	   Set @ExistsInTbl_2 = 1; -- to get out of the loop
	else
	   Set @LastTbl_1 = @LastTbl_1 + 1;  -- add 1 to search for next
  
end

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LVL 50

Accepted Solution

by:
Vitor Montalvão earned 500 total points
ID: 40434504
You just need to change the '=' to '>':
@LastTypPlusOne = Select MAX(Type) From Tb_1

 Insert Into Tbl1(Type, Wt)
 Select Type, Wt
 From Tbl2
 Where Type > @LastTypPlusOne

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LVL 34

Expert Comment

by:Mike Eghtebas
ID: 40435084
re:> You just need to change the '=' to '>':

In that case,it will insert all from Tbl_2 (maybe this is what is what Saxitalis wants):

Tbl 2:

Type    Wt
1           10.0
2           10.2
3           11.3
7           22.5
8           12.0
12          14.3
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LVL 50

Expert Comment

by:Vitor Montalvão
ID: 40435088
Not all but everything greater than 3 (in this example).
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LVL 34

Expert Comment

by:Mike Eghtebas
ID: 40435094
I was just adding the next equal or greater than "@LastTypPlusOne + 1" as Saxitalis puts it). This is what I was trying to achieve. But when I read it again, I see my mistake: "I want to add new records in Tbl 2 to Tbl1 based on the last record in Tbl1."
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Author Closing Comment

by:Saxitalis
ID: 40438947
Yup - I tried that first Victor but records would not sort correctly so I was trying to import one record at a time.

 I finally realized the reason records would not sort was because I was converting the column in question to VARCHAR data type when accessing via a linked server via C# code. I solved this bypopulating  the table coming in through the linked server into a temp table with INT data type. Then performed the query on the temp table.

I am excepting your solution because it made me go back and think about "why"

Thanks!
John
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