比較來自不同表格的2列

Question

我有兩張表，每列中有相同的列。讓我們稱它爲顏色。我如何比較兩者以顯示錶B中不在表A中的獨特顏色？

Answer 1

select b.color 
    from tbl1 b 
where not exists (select * from tbl2 a where b.color=a.color) 

Answer 2

SELECT b.color AS color FROM tableB b 
LEFT JOIN tableA a ON a.color = b.color 
WHERE a.color IS NULL;