>This is one to one relationship and in the other case it's not 1 to 1. But I would not write this UPDATE that same way also. I'd rather use CTE and ROW_NUMBER approach.
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>It's a bad idea to write UPDATE that way. Check out this blog post
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>Dear FROM clause...
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>This is one of my many favorites of his blogs.

Yes, I thought of that but in this case, the BusinessTime is not in relation with the Client table. It is only used to received the first and last date and use that as parameters to get a subset of records.

Could you provide an example on how you would establish this 1 to 1 relationship in a CROSS APPLY approach I believe?