You are inserting a table - each select is a row, each comma delimited item in the selects is a field. Each select has 2 fields, while the parenthetical field list has 3 fields. Try something like:
INSERT INTO attendence (FName, LName, Mark)
$FName, $LName, $Mark
To use your select test setup:
INSERT INTO attendence (FName, LName, Mark)
SELECT 'FName1', 'LName1', 1
UNION ALL
SELECT 'FName2', 'LName2', 2
UNION ALL
SELECT 'FName3', 'LName3', 3
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…