SQL Returning the same Data or Repeats

Question

Updating a Column from another table and my attempts are queuing the same data that's already in Speedlink_ID I am trying to Update CON_SP_ID from CON_SP_ID Table 1 CON_SP_ID all rows are blank or NULL Table 2*Speedlink_ID* has the data

Both columns have the same amount of rows.

ATTEMPT 1 - Returns no updated data.

UPDATE t1
SET    CON_SP_ID = t2.Speedlink_ID
FROM   dbo.Data1 AS t1
      INNER JOIN  dbo.Data2 AS t2
      ON t1.CON_SP_ID = t2.[Speedlink_ID]

SELECT TOP (1000) [CON_SP_ID]
FROM Data1

ATTEMPT 2

UPDATE t -- alias of table you are updating
SET    CON_SP_ID = d.Speedlink_ID
FROM   Data1 t
       join Data2 d on d.Speedlink_ID = t.CON_SP_ID


SELECT TOP (1000) [CON_SP_ID]
FROM [Data1]

ATTEMPT 3

UPDATE [Data1]
SET    [Data1].CON_SP_ID = (

            SELECT CON_SP_ID

            FROM         [DATA2]

            WHERE   [Data1].CON_SP_ID = [DATA2].CON_SP_ID)


SELECT TOP (1000) [CON_SP_ID]
FROM [Data1]

ATTEMPT 4 - Repeats first ROW of [DATA2].[Speedlink_ID] to the end of the table

UPDATE [Data1]
SET    [Data1].CON_SP_ID =  [DATA2].[Speedlink_ID]

            FROM         [DATA2]        

    SELECT TOP (1000) [CON_SP_ID]
FROM [Data1]

Shows Repeats

Answer 1

Thanks @avery_larry

I did realize you needed a column that is the same on both tables. Subnet is in the same sort order / entered in the same way as my 2nd table. I needed to match row for row using the subnet and my KEY because its a Unique number.

Still learning, thx every one

UPDATE [Data1]
SET   [Data1].[CON_SP_ID] = [Data2].[Con_SP_ID]

FROM
            dbo.Data1 as Data1
INNER JOIN
            dbo.Data2 AS Data2  

ON 
           Data1.Subnet = Data2.Subnet

SELECT TOP (1000) [CON_SP_ID]
FROM [Data1]