SQL：更新中内部联接的错误

Question

我无法在我的请求中发现问题。这是我的请求和2表：

UPDATE RESERVATION inner join client on reservation.numcl = client.numcl
SET reservation.numcl2 = client.numcl2;

错误：

   => [42000][971] ORA-00971: missing SET keyword

1. 表客户端 Client table

2. 预订客户 reservation table

解决方案：

UPDATE RESERVATION SET reservation.numcl2 = (select client.NUMCL2
                                             from CLIENT
                                             where client.NUMCL= RESERVATION.numcl);

Answer 1

Oracle不支持join中的update（至少是明确的）。您想要做的事情的等价物是：

UPDATE RESERVATION r
    SET numcl2 = (select client.NUMCL2
                  from CLIENT c
                  where c.NUMCL = r.numcl
                 )
    WHERE EXISTS (SELECT 1 FROM client c WHERE c.NUMCL = r.numcl);

如果你想处理没有匹配的情况，exists很重要。