Convert to DateTime

I have a date filed 12/26/2006 and a time field 7:00am. How can I combine them in my select statement and get a DateTime field.

Using SQL Server?

SELECT CONVERT(VARCHAR(10), MyDateField) + Convert(VARCHAR(12), MyTimeField) As MyDateTimeField
FROM MyTable

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I forgot to add a space between the date and time:

SELECT CONVERT(VARCHAR(10), MyDateField) + ' ' + CONVERT(VARCHAR(12), MyTimeField) As MyDateTimeField
FROM MyTable

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What are exact definitions of those fields in database?