DTA is... um... I'll find a polite word for it in a moment, hang on.
....
DTA is a best effort guess from an app to try to help you figure out good methods for approaching your data from a single point of view. It's really, really bad at it though. It's not horrible for OLAP systems which are typically write once/read 3 billion times, but OLTP systems that implement all the recommendations would bog down.
Your best bet is to analyze your optimization plans, determine what your access methods can be, and then reviewing your existing tables. Sometimes simply including a single column into an existing index is the answer. Sometimes rebuilding the table from scratch with a clustered index that isn't the PK is.
I would recommend that you post your query, the underlying DDL for the tables, and the execution plan here, and the good folks round these parts will help you find your solution.
Never stop learning, even if it hurts. Ego bruises are practically mandatory as you learn unless you've never risked enough to make a mistake.
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