sql - Derby 数据库 : sql update the results of a select statement

Question

我有两个表:

元素:

ID (int. key)
TYPE (String)

ELEMENT_ATTRIBUTES:

ELEMENT_ID (int)
ATTR_NAME (String)

(我忽略了原始表中的字段，这些字段对于这个问题不是必需的)

我想做这样的事情:

UPDATE ELEMENT e, ELEMENT_ATTRIBUTES a
SET a.ATTR_NAME='new name'
WHERE e.ID = a.ELEMENT_ID
  AND e.TYPE = 'a specific type'
  AND a.ATTR_NAME = 'old name'

这在 derby sql 中可能吗？

Answer 1

查看the Derby Reference Manual on the UPDATE statement语法是:

{
    UPDATE table-Name [[AS] correlation-Name]
        SET column-Name = Value
        [ , column-Name = Value} ]*
        [WHERE clause] |
    UPDATE table-Name
        SET column-Name = Value
        [ , column-Name = Value ]*
        WHERE CURRENT OF
}

所以不，你不能像你的问题那样执行查询。您需要将其修改为:

UPDATE ELEMENT_ATTRIBUTES a
SET a.ATTR_NAME='new name'
WHERE a.ATTR_NAME = 'old name'
AND EXISTS (SELECT 1 
            FROM ELEMENT e 
            WHERE a.ELEMENT_ID = e.ID AND e.TYPE = 'a specific type')