我有了这个表耐心,必须查询它MySQL的使用子查询与更新
Update the database in order to provide a 3% discount to all patients in a room that has more than 2 patients.
表是由如下:
CREATE TABLE patient (
sin varchar(20) NOT NULL,
disease varchar (20),
bed varchar (20),
room varchar (20),
hospital varchar (0),
fee varchar(20),
entry_date date NOT NULL,
exit_date date,
CONSTRAINT FOREIGN KEY (sin) REFERENCES person(sin)
)
所以我想找到所有患者'房间出现超过2名患者,然后更新表格:
UPDATE patient C
INNER JOIN patient D ON C.sin=D.sin and D.sin IN (SELECT A.sin
FROM patient A
WHERE 2 < (SELECT COUNT(B.sin)
FROM patient B
WHERE A.hospital=B.hospital and A.room=B.room and A.exit_date IS NULL and B.exit_date IS NULL)
)
SET C.fee=C.fee*0.97
问题是我得到的错误:
You can't specify target table 'C' for update in FROM clause
有没有办法使用子查询更新? 非常感谢。
工作完美,只是组'医院,房间'而不是团体医院,房间。如果你可以修改你的答案,所以它是完美的 非常感谢! – icosac