使用多个连接将选择变成更新 Postgres

Question

所以这是我第一次想对具有多个连接的查询进行更新。

数据库 = Postgres v.10

这是我迄今为止尝试过的：

update table1 t1 set t4.datum = t1.datum
from table1 t1
inner join table3 t3 on t3.id = t1.id
inner join table4 t4 on t4.id = t3.t4_id
where t3.id = 550 and t4.scale is not null and t4.datum is null

错误：SQL 错误 [42712]：错误：表名“t1”指定了多次

下一次尝试：

update table1 t1 set t4.datum = t.datum
from table1 t
inner join table3 t3 on t3.id = t.id
inner join table4 t4 on t4.id = t3.t4_id
where t3.id = 550 and t4.scale is not null and t4.datum is null

错误：SQL 错误 [42703]：错误：关系“table1”的列“t4”不存在 职位：28

最后一次尝试：

update table1 t1 set t4.datum = t.datum
from table1 t
inner join table3 t3 on t3.id = t.id
inner join table4 t4 on t4.id = t3.t4_id
where t1.id = t.id and t3.id = 550 and t4.scale is not null and t4.datum is null

错误：SQL 错误 [42703]：错误：关系“table1”的列“t4”不存在 职位：28

我做错了什么？

Answer 1

您不应在 FROM 子句中重复 UPDATE 的目标表。所以类似的东西。分配set t4.datum = t.datum 也似乎是错误的。如果您想更新table1，则不能在作业左侧引用t4。此外，目标列在 SET 部分内不能是“表限定”（因为很清楚是指哪个表的列）

所以我认为您正在寻找这样的东西：

update table1 t1 
   set datum = t4.datum
from table3 t3 
  inner join table4 t4 on t4.id = t3.t4_id
where t1.id = t3.id 
  and t3.id = 550 
  and t4.scale is not null 
  and t4.datum is null

Answer 2

在 FROM 子句中引用表的别名，然后在整个过程中使用它。我认为我正确地编辑了这个：

update t1 set t4.datum = t1.datum
from table1 t1
inner join table3 t3 on t3.id = t1.id
inner join table4 t4 on t4.id = t3.t4_id
where t3.id = 550 and t4.scale is not null and t4.datum is null;

Answer 3

我认为您的问题是因为想从表 table1 更新 t4.datum。

您应该将设置列 t4.datum = t1.datum 更改为 t1.datum = t4.datum 因为您想要更新 table1（更新查询：update table1 t1）和 t4.datum 不引用 table1

应该像下面这样改变查询（如果你想更新table1）：

update table1 t1 set t1.datum = t4.datum
from table1 t
inner join table3 t3 on t3.id = t.id
inner join table4 t4 on t4.id = t3.t4_id
where t1.id = t.id and t3.id = 550 and t4.scale is not null and t4.datum is null

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已编辑

查询更新table4：

update table4 u_t4 set datum = t1.datum
from table1 t1
inner join table3 t3 on t3.id = t1.id
inner join table4 t4 on t4.id = t3.t4_id
where t4.id = u_t4.id and t3.id = 550 and t4.scale is not null and t4.datum is null