if you are intending to add rows then use MERGE as Sean suggests.

If you are only intending to update data then just use UPDATE with a join on the tables.

some sample code below....but as you say "Table 2 also has the same but latest supplier information and same 24 columns" ...so whats the requirement for Table 1...or is this just homework?

SELECT TOP 100

SupplierID = IDENTITY(INT, 1, 1),

SerialID = CAST(Abs(Checksum(Newid()) % 90000 + 1) AS INT)

INTO dbo.TAB1

FROM sys.all_columns ac1

/* create copy of TAB1 */

SELECT * INTO TAB2 FROM TAB1

/* set every 5th supplier serialId to NULL */

UPDATE TAB1

SET SerialID = NULL

WHERE (SupplierID % 5 = 0)

/*check to see missing matches */

SELECT TAB1.SupplierID, TAB1.SerialID AS TAB1SID, TAB2.SerialID AS TAB2SID

FROM TAB1 INNER JOIN

TAB2 ON TAB1.SupplierID = TAB2.SupplierID

AND ISNULL(TAB1.SerialID,0) <> TAB2.SerialID

/* update TAB1 SerialID from TAB2*/

UPDATE TAB1

SET SerialID = TAB2.SerialID

FROM TAB1 INNER JOIN

TAB2 ON TAB1.SupplierID = TAB2.SupplierID

WHERE (TAB1.SerialID IS NULL)

/*check to see missing matches */

SELECT TAB1.SupplierID, TAB1.SerialID AS TAB1SID, TAB2.SerialID AS TAB2SID

FROM TAB1 INNER JOIN

TAB2 ON TAB1.SupplierID = TAB2.SupplierID

AND ISNULL(TAB1.SerialID,0) <> TAB2.SerialID