What is the difference between "Tachris Es Zar'i" and "Tashmid Es Shmi"?
Radak: They are the same. He doubled the matter to strengthen it. Children are the name of the fathers, and through them [the fathers] are remembered. We find "v'Hichrati l'Bavel Shem u'Sh'ar", "Lo Yikares [v'Lo Yishamed] Shmo" (Yeshayah 14:22, 48:19).
Alshich: If he would leave alive only female descendants, he did not eradicate his seed, but he wiped out his name, for their children will called on the name of their fathers.
Did David swear about both of these?
Malbim: Meforshim say that he swore only about the latter, for he gave Sha'ul's descendants to the Giv'onim! This is wrong. The Giv'onim killed them; David did not!