CREATE TABLE table_25289 ("Constituency" TEXT, "Winner" TEXT, "Party" TEXT, "Margin" FLOAT, "Runner-up a" TEXT, "Party a" TEXT)

What is the margin when periyakulam is the constituency?
SELECT "Margin" FROM table_25289 WHERE "Constituency" = 'Periyakulam'
SELECT "Margin" FROM "table_25289" WHERE "Constituency" = 'Periyakulam'