Table: election_results_1971
Columns: constituency
winner
party
margin
runner_up_a
party_a

Question: What is the margin when k. balathandayutham is the winner?
SQL: SELECT MAX("margin") FROM election_results_1971 WHERE "winner" = 'K. Balathandayutham'

Question: What is the margin when periyakulam is the constituency?
SQL: SELECT "margin" FROM election_results_1971 WHERE "constituency" = 'Periyakulam'