insert select 過濾掉重複數據

INSERT INTO SELECT 語句從一個表複製數據，然後把數據插入到一個已存在的表中。

table1和table2表結構一樣時：

INSERT INTO table2
SELECT * FROM table1;

table1和table2表結構不一樣時：

INSERT INTO table2(field1,field2,field3)
SELECT field1,field2,field3 FROM table1;

NOT EXISTS 過濾掉重複的數據：

INSERT INTO
	table1(field1,field2,field3)
SELECT field1,field2,field3 FROM table2 a
WHERE NOT EXISTS (SELECT * FROM table1 b where a.field1=b.field1)