The last verse of Psalm 20 offers an interesting glimpse into issues of translation without causing too much impact in interpretation.
Here is the Hebrew with a literal translation followed by the main English options:
יְהוָ֥ה הוֹשִׁ֑יעָה הַ֝מֶּ֗לֶךְ יַעֲנֵ֥נוּ בְיוֹם־קָרְאֵֽנוּ׃
Yahweh save the-king may-he-answer-us in-the-day-of-our-calling. (Heb)
O LORD, save the king! May he answer us when we call. (ESV)
Save, O LORD; May the King answer us in the day we call. (NASB, KJV)
Give victory to the king, O LORD; answer us when we call. (RSV, NIV)
If you read carefully you will see that there are two points of difference, one in each half of the verse. In the first half of the verse there is the question as to whether the word “the king” is the direct object of “Lord, save” or the subject of the verb “May he answer us” in the second half of the verse. The ambiguity is created by the fact that Hebrew does not have punctuation to make the break in the thought clear. I think the KJV may have taken the option it does because it makes the verse more overtly Christological.
The second difference has to do with the subject of the verb “answer” in the second half of the verse. Who’s the “he?” The first two options follow the Hebrew in making the subject of the verb “He” as the verb form indicates. The third English option above, represented by the RSV and NIV, makes the subject of the verb “answer” out to be “you”, referring to Yahweh from the first half of the verse. It is understandable why they have done this. Having made the first half of the verse a direct address to the Yahweh, “Lord, save the King” and not wanting to say “May the king answer us when we call” because it sounds like the people would be praying to the king, they opt to see the referent of the verb “answer” to be “The Lord” even though that necessitates changing the verb from “may-he-answer” to “may-you-answer.”
What do I think? Regarding the first issue, I think “Lord, save the king!” is the best because it fits best with the theme of the psalm and because it balances the lines in the verse into 2 three word phrases. Regarding the second, I think the best explanation is that the second half is a summary phrase that echoes the early verses of the psalm. This way the subject of “May-he-answer-us” can still be Yahweh not the king, just as those early verses were expressed to Yahweh. It also explains how the verse can shift from direct address to third person.
Does it matter? Well, from a NT perspective, not too much. Christ is Lord and Christ is the King!
 Hyphens indicate multiple words translating one Hebrew word.
 For Spanish speakers this is like the difference between estás, you are, and está, he is.