替代Oracle的minus写法
1 SELECT * 2 FROM Table1 a 3 LEFT JOIN Table2 b 4 ON a.Col1 = b.Col1 AND a.Col2 = b.Col2 5 WHERE b.Col1 IS NULL
适用非Oracle的数据库，还有一种写法总感觉没这优雅，因为用了 NOT EXISTS
1 SELECT * 2 FROM Table1 3 WHERE NOT EXISTS ( 4 SELECT * 5 FROM Table2 6 WHERE Col1 = Table1.Col1 7 AND Col2 = Table1.Col2 8 )
