A JOIN is preferred over the older-style WHERE clause, although with an INNER JOIN they should function the same either way:
INSERT INTO myTable
(ID,someData,someData2)
SELECT
tempTable.matchID as ID, myTable.someData, myTable.someData2
FROM myTable
INNER JOIN tempTable ON myTable.ID = tempTable.ID
SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".