Question

我有一张桌子“queued_items”。当前“user_id”和“item_id”不正确，但存储在其他表中：users.imported_id和items.imported_id

尝试从其他表中获取imported_id并进行更新。这是我试过的东西

UPDATE queued_items
SET queued_items.user_id = users.id,
    queued_items.item_id = items.id
FROM queued_items
INNER JOIN users ON queued_items.user_id = users.imported_id
INNER JOIN items ON queued_items.item_id = items.imported_id

出现此错误：

Error : ERROR:  table name "queued_items" specified more than once

尝试删除FROM行，出现此错误：

Error : ERROR:  syntax error at or near "INNER"
LINE 4: INNER JOIN users ON queued_items.user_id = users.imported_id
         ^

我还尝试在FROM和JOIN条件中添加别名

UPDATE queued_items
SET queued_items.user_id = users.id,
    queued_items.item_id = items.id
FROM queued_items as qi
INNER JOIN users ON qi.user_id = users.imported_id
INNER JOIN items ON qi.item_id = items.imported_id

出现此错误：

Error : ERROR:  column "queued_items" of relation "queued_items" does not exist
LINE 2: SET queued_items.user_id = users.id,
            ^

有什么想法吗？（postgres 9）

PS 尝试避免此子查询：

UPDATE queued_items
SET user_id = (SELECT id FROM users WHERE queued_items.user_id = users.imported_id),
    item_id = (SELECT id FROM items WHERE queued_items.item_id = items.imported_id)

...因为它很疯狂

Answer 1

试试这个：

UPDATE queued_items
SET user_id = users.id,
    item_id = items.id
FROM users, items
WHERE queued_items.user_id = users.imported_id
  AND queued_items.item_id = items.imported_id

是的，老学校加入了条件。

Answer 2

From postgres site

UPDATE [ ONLY ] table [ [ AS ] alias ]
    SET { column = { expression | DEFAULT } |
          ( column [, ...] ) = ( { expression | DEFAULT } [, ...] ) } [, ...]
    [ FROM from_list ]
    [ WHERE condition | WHERE CURRENT OF cursor_name ]
    [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]

* from_list *

表表达式列表，允许其他表中的列将显示在 WHERE条件和更新表达式。这类似于可以指定的表的列表在SELECT的FROM子句中声明。注意目标表不得出现在from_list中，除非你打算自我加入（在它必须出现在哪种情况下 from_list中的别名。

Answer 3

UPDATE queued_items
SET user_id = users.id,
    item_id = items.id
FROM queued_items as QI
INNER JOIN users ON QI.user_id = users.imported_id
INNER JOIN items ON QI.item_id = items.imported_id

Answer 4

使用子查询语句并将索引添加到这些列。

Answer 5

我不得不尝试使用列/表命名，并最终使它起作用。我必须：

在目标SET列中省略表名
确保我别名为要更新的表

您的等效项将是：

UPDATE queued_items
SET user_id = users.id,
    item_id = items.id
FROM queued_items as alias_queued_items
INNER JOIN users ON alias_queued_items.user_id = users.imported_id
INNER JOIN items ON alias_queued_items.item_id = items.imported_id

而不是：

UPDATE queued_items
SET queued_items.user_id = users.id,
    queued_items.item_id = items.id
FROM queued_items
INNER JOIN users ON queued_items.user_id = users.imported_id
INNER JOIN items ON queued_items.item_id = items.imported_id

Answer 6

您应该可以在UPDATE之后将名称更改为别名。您还可以在set子句中使用别名。这意味着您也可以在JOIN子句中设置它们。

UPDATE qi 
SET qi.user_id = us.id,
    qi.item_id = itms.id
FROM queued_items qi
INNER JOIN users us ON qi.user_id = us.imported_id
INNER JOIN items itms ON qi.item_id = itms.imported_id

Answer 7

您不需要FROM子句。删除“FROM queued_items”即可完成。

错误：错误：多次指定表名

7 个答案: