SQL Query: IF ELSE Statement - Insert if not exist otherwise Update

Scenario:

I want to INSERT if NOT Exist otherwise I want to UPDATE recrod

Solution:

Example1:

IF EXISTS (SELECT NULL FROM MyTable WHERE ScorerID = @Blah AND CONVERT(VARCHAR, DateCreated, 101) = CONVERT(VARCHAR, GETDATE(), 101))

    UPDATE MyTable SET blah blah blah

ELSE

    INSERT INTO MyTable blah blah blah

Example2:

INSERT INTO AggregatedData (datenum,Timestamp)

VALUES ("734152.979166667","2010-01-14 23:30:00.000")

ON DUPLICATE KEY UPDATE

  Timestamp=VALUES(Timestamp)