基本上,我想这样做:

update vehicles_vehicle v 
    join shipments_shipment s on v.shipment_id=s.id 
set v.price=s.price_per_vehicle;

我很确定这在MySQL(我的背景)中可以工作,但在postgres中似乎不起作用。我得到的错误是:

ERROR:  syntax error at or near "join"
LINE 1: update vehicles_vehicle v join shipments_shipment s on v.shi...
                                  ^

当然有一个简单的方法来做到这一点,但我找不到合适的语法。那么,我该如何在PostgreSQL中写这个呢?


当前回答

UPDATE语法为:

[ WITH [ RECURSIVE ] with_query [, ...] ]
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 ] [, ...] ]

在你的情况下,我认为你想要的是:

UPDATE vehicles_vehicle AS v 
SET price = s.price_per_vehicle
FROM shipments_shipment AS s
WHERE v.shipment_id = s.id 

或者如果你需要连接两个或多个表:

UPDATE table_1 t1
SET foo = 'new_value'
FROM table_2 t2
    JOIN table_3 t3 ON t3.id = t2.t3_id
WHERE
    t2.id = t1.t2_id
    AND t3.bar = True;

其他回答

对于那些真正想要做JOIN的人,你也可以使用:

UPDATE a
SET price = b_alias.unit_price
FROM      a AS a_alias
LEFT JOIN b AS b_alias ON a_alias.b_fk = b_alias.id
WHERE a_alias.unit_name LIKE 'some_value' 
AND a.id = a_alias.id;

如果需要,可以在等号右侧的SET部分中使用a_alias。 等号左边的字段不需要表引用,因为它们被认为来自原始的“a”表。

开始吧:

update vehicles_vehicle v
set price=s.price_per_vehicle
from shipments_shipment s
where v.shipment_id=s.id;

我能做到的最简单。

在PostGRE SQL / AWS (SQL工作台)中使用另一个表更新一个表。

在PostGRE SQL中,你需要在UPDATE Query中使用join:

UPDATE TABLEA set COLUMN_FROM_TABLEA = COLUMN_FROM_TABLEB FROM TABLEA,TABLEB WHERE FILTER_FROM_TABLEA = FILTER_FROM_TABLEB;

Example:
Update Employees Set Date_Of_Exit = Exit_Date_Recorded , Exit_Flg = 1 From Employees, Employee_Exit_Clearance Where Emp_ID = Exit_Emp_ID

表A - Employees列表A - Date_Of_Exit,Emp_ID,Exit_Flg表B是- Employee_Exit_Clearance列表B - Exit_Date_Recorded,Exit_Emp_ID

1760行受影响

执行时间:29.18秒

在上面所有的答案中添加一些非常重要的东西,当你想要更新连接表时,你可能会遇到两个问题:

您不能使用您想要更新的表来JOIN另一个表 Postgres希望在JOIN之后有一个ON子句,因此不能只使用where子句。

这意味着基本上,以下查询是无效的:

UPDATE join_a_b
SET count = 10
FROM a
JOIN b on b.id = join_a_b.b_id -- Not valid since join_a_b is used here
WHERE a.id = join_a_b.a_id
AND a.name = 'A'
AND b.name = 'B'
UPDATE join_a_b
SET count = 10
FROM a
JOIN b -- Not valid since there is no ON clause
WHERE a.id = join_a_b.a_id 
AND b.id = join_a_b.b_id
a.name = 'A'
AND b.name = 'B'

相反,你必须像这样使用FROM子句中的所有表:

UPDATE join_a_b
SET count = 10
FROM a, b
WHERE a.id = join_a_b.a_id 
AND b.id = join_a_b.b_id 
AND a.name = 'A'
AND b.name = 'B'

这对一些人来说可能很简单,但我被这个问题困住了,想知道发生了什么,所以希望它能帮助到其他人。

我举个例子再解释一下。

任务:正确的信息,在哪里abiturients(即将离开中学的学生)提交申请大学早于他们获得学校证书(是的,他们获得证书早于他们颁发的证书(指定证书日期)。因此,我们将增加申请提交日期,以适应证书颁发日期。

因此。下一个mysql类语句:

UPDATE applications a
JOIN (
    SELECT ap.id, ab.certificate_issued_at
    FROM abiturients ab
    JOIN applications ap 
    ON ab.id = ap.abiturient_id 
    WHERE ap.documents_taken_at::date < ab.certificate_issued_at
) b
ON a.id = b.id
SET a.documents_taken_at = b.certificate_issued_at;

以这样的方式变得像postgresql

UPDATE applications a
SET documents_taken_at = b.certificate_issued_at         -- we can reference joined table here
FROM abiturients b                                       -- joined table
WHERE 
    a.abiturient_id = b.id AND                           -- JOIN ON clause
    a.documents_taken_at::date < b.certificate_issued_at -- Subquery WHERE

可以看到,原来的子查询JOIN的ON子句已经变成了WHERE条件之一,由AND与其他子查询连接,这些子查询已经从子查询中移动,没有任何变化。并且不再需要将表与自身连接(就像在子查询中那样)。