This Bible contradiction is from the Skeptic's Annotated Bible.
Michal had no child.
2 Samuel 6:23 View context
Therefore Michal the daughter of Saul had no child unto the day of her death.
Michal had five children.
2 Samuel 21:8 View context
But the king took the two sons of Rizpah the daughter of Aiah, whom she bare unto Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she brought up for Adriel the son of Barzillai the Meholathite: