Question

EDIT: I have written it a bit wrong gill change my Q

I’m a newbie with SQL and I have a Q..

I made 2 Temp. Tables.
Each has 25 Rows.(DateValue)

I want to combine this 2 tables in a third table..
First Table is [From]
Second Table is [To]…
Both tables have different values

I want to get it like this:

From| To |
1111|2222
2222|3333
3333|4444

etc..

I use this simple Query

Create Table #T3
( 
   [From] Datetime
   ,[To] Datetime
)

INSERT  Into #T3
SELECT Distinct #T1.[From], #T2.[To]
From #T1,#T2
Where #T1.[From] is not null
And #T2.[To] is not null

Select * from  #T3

Drop Table #T3
Drop Table #T2
Drop Table #T1

But my results are like this

From| To |
1111|1111
1111|2222
1111|3333
2222|1111
2222|2222
2222|3333

It multiplies the first field with the second wich gives me alot more records back..

Any help ?
THANKS !

Answer 1

After the OP’s edit

This may work as you want (which is not entirely clear):

INSERT INTO #T3 
  SELECT #T1.[From]
       , MIN(#T2.[To]) 
  FROM #T1
    JOIN #T2
      ON #T1.[From] < #T2.[To]
  GROUP BY #T1.[From]

---

Using

FROM T1, T2

results in all combinations or rows of T1 and T2. It’s called a cross product and (properly) used with CROSS JOIN, like this:

FROM T1 CROSS JOIN T2

---

When you want to join the two tables based on a condition (and not get the cross product), you use a JOIN or INNER JOIN (these two are same thing):

FROM T1 JOIN T2
  ON T1.[From] = T2.[To]

will get you all rows combinations where T1.From matches T2.To (on equality). I suppose you wanted to match every row of T1 with the row of T2 where T2.To was just larger than T1.From so I used the “smaller than” < operator instead of the “equality” = operator.

The GROUP BY and MIN() were added to get only the one with smallest T2.To from those rows.