SELECT * FROM mytable WHERE column3 IS NOT NULL;
o ¿a qué te refieres con algo así?
SELECT * FROM mytable WHERE column3 = 'yes' AND column1 IS NOT NULL;
SELECT * FROM mytable WHERE column3 IS NOT NULL;
o ¿a qué te refieres con algo así?
SELECT * FROM mytable WHERE column3 = 'yes' AND column1 IS NOT NULL;