WHERE met datum

$query="SELECT * FROM agenda WHERE datum = morgen
		GROUP BY datum,opdracht,vak,opgave,opdracht
        ";

$query="SELECT * FROM agenda WHERE datum = morgen
		GROUP BY datum,opdracht,vak,opgave,opdracht
        ";

SELECT something FROM tbl_name
    -> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col;

SELECT something FROM tbl_name
    -> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col;

$query="SELECT * FROM agenda
        WHERE datum='DATE_SUB(CURDATE(),INTERVAL 30 DAY)' 
		GROUP BY datum,opdracht,vak,opgave,opdracht
        ";

$query="SELECT * FROM agenda
        WHERE datum='DATE_SUB(CURDATE(),INTERVAL 30 DAY)' 
		GROUP BY datum,opdracht,vak,opgave,opdracht
        ";

FOUT: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '
WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) GROUP BY datum,opd' at line 1

FOUT: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '
WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) GROUP BY datum,opd' at line 1