Inner Join:
Left Outer Join:
Right Outer Join:
Full Join:
Cross Join：
SELECT t1.attrs ,t2.attrs FROM t1 CROSS JOIN t2
使用Join更新表：
UPDATE table1 SET attr2 WHERE attr1 IN (SELECT table2.attr1 FROM table1 INNER JOIN table2 ON table1.attr1 =table2.attr1 )
)