条件不匹配的更新语句

Question

我有一个更新查询如下-

udate table1 tbl_out
set column1 =
    (select colValue from table1 t1, table2 t2
    where table1.product_id = table2.product_id
    and t1.id = tbl_out.id)
where tbl_out.column1 is null;

这很好用。但是有些列的 table1.product_id 值为 null。 所以对于这些记录 where table1.product_id = table2.product_id 条件不满足，记录没有更新。

我尝试按如下方式添加此条件 -

where (table1.product_id = table2.product_id OR table1.product_id is null)
and t1.id = tbl_out.id

但这将返回多于 1 行，以上更新语句将失败。 我知道在这种情况下可能很简单但无法弄清楚的问题。

有人可以帮我吗？

Answer 1

   udate table1 tbl_out
 set column1 =
(select colValue from table1 t1, table2 t2
where nvl(table1.product_id,table2.product_id) = table2.product_id
and t1.id = tbl_out.id)
where tbl_out.column1 is null;

Answer 2

我认为您正在寻找一个简单的相关子查询，这意味着您不需要子查询中的JOIN：

update table1 tbl_out
    set column1 = (select t2.colValue
                   from table2 t2
                   where t2.product_id = tbl_out.product_id
                  )
    where tbl_out.column1 is null;

您可能还需要一个exists 子句：

update table1 tbl_out
    set column1 = (select t2.colValue
                   from table2 t2
                   where t2.product_id = tbl_out.product_id
                  )
    where tbl_out.column1 is null and
          exists (select 1
                  from table2 t2
                  where t2.product_id = tbl_out.product_id
                 );

编辑：

如果您在 table2 中有一个 NULL 值，并且您试图将其视为有效密钥：

update table1 tbl_out
    set column1 = (select t2.colValue
                   from table2 t2
                   where t2.product_id = tbl_out.product_id or
                         (t2.product_id is null and tbl_out.product_id is null)
                  )
    where tbl_out.column1 is null;