连接运算是 8种关系运算 中的一种。
五种JOIN方式
1.INNER JOIN or JOIN
2.OUTER JOIN
2.1LEFT OUTER JOIN or LEFT JOIN
2.2RIGHT OUTER JOIN or RIGHT JOIN
2.3FULL OUTER JOIN or FULL JOIN
3.NATURAL JOIN
4.CROSS JOIN
5.SELF JOIN
连接运算是 8种关系运算 中的一种。
1.INNER JOIN or JOIN
2.OUTER JOIN
2.1LEFT OUTER JOIN or LEFT JOIN
2.2RIGHT OUTER JOIN or RIGHT JOIN
2.3FULL OUTER JOIN or FULL JOIN
3.NATURAL JOIN
4.CROSS JOIN
5.SELF JOIN