oracle中update多表关联查询

在Oracle中，可以使用子查询或MERGE语句实现多表关联更新。下面是两种实现方式的示例：

1. 使用子查询：

UPDATE table1
SET column1 = (SELECT column2
               FROM table2
               WHERE table1.key = table2.key),
    column3 = (SELECT column4
               FROM table3
               WHERE table1.key = table3.key)
WHERE EXISTS (SELECT 1
              FROM table2
              WHERE table1.key = table2.key)
   OR EXISTS (SELECT 1
              FROM table3
              WHERE table1.key = table3.key);

2. 使用MERGE语句：

MERGE INTO table1
USING (SELECT key, column2, column4
       FROM table2
       JOIN table3 ON table2.key = table3.key) t
ON (table1.key = t.key)
WHEN MATCHED THEN
    UPDATE SET table1.column1 = t.column2,
               table1.column3 = t.column4;

请根据你的具体需求选择适合的方式进行多表关联更新。