'Where'条件多列组合为一条规则

Question

我是 postgres.I 的新手，需要在我的 table 之一的 postgres 中创建规则。我正在使用 postgres 11.4.

这是我为此使用的语法：

      CREATE RULE flagrule AS ON insert TO ms
  WHERE NEW.a = OLD.a and new.b = old.b and new.c = old.c and
new.d = old.d and new.e = old.e

DO instead
update ms set flag = 0  where 
a = NEW.a and
b= new.b and
c = new.c and
d = new.d and
e = new.e;

并出现以下错误：

     SQL Error [42P01]: ERROR: invalid reference to FROM-clause entry for 
   table "old"
    Hint: There is an entry for table "old", but it cannot be referenced 
      from this part of the query.
     Position: 76

我 google 对此有很多了解，但我在 'where' 子句中仅获得了单列条件的示例。如果有人对此有任何想法，请告诉我。任何帮助将不胜感激。

Answer 1

The documentation 状态：

Within <strong>condition</strong> and <strong>command</strong>, the special table names NEW and OLD can be used to refer to values in the referenced table. NEW is valid in ON INSERT and ON UPDATE rules to refer to the new row being inserted or updated. OLD is valid in ON UPDATE and ON DELETE rules to refer to the existing row being updated or deleted.

由于您正在尝试创建 ON INSERT 规则，因此您不能使用 OLD。这到底是什么意思？

'Where'条件多列组合为一条规则

'Where' condition on the combination of multiple columns for a rule

postgresql

rules