它在哪里被权威地记录了（expr，expr，...）语法是什么？ [英] Where is it authoritatively documented what the (expr,expr,...) syntax does?

问题描述

在另一个问题中，断言以下条件条件是等价的：

In another question, it was asserted that the following conditional criteria are equivalent:

(a,b,c,d) != (1,2,3,4)                  -- (1)
(a != 1 OR b != 2 OR c != 3 OR d != 4)  -- (2)

（a，b，c，d）构造的解析规则（注意它不是一个子查询）是 simple_expr 和这里有一个语法生产。

The parsing rule for the (a,b,c,d) construct (note that it is not a subquery) is simple_expr and there's a grammatical production for it there.

但是，我找不到任何文档上述条件（1）的行为和我的直觉告诉我，这不是相当于（2 ）。

However, I cannot find any documentation at all for the behaviour of the above conditional (1), and my gut is telling me that it is not equivalent to (2).

• 此表达式在此上下文中的行为在

• Where is the behaviour of this expression in this context documented?

^{（答案必须权威的来源，或者说不存在，而且我们必须通过经验证据推断表达的行为。）}

^{(Answers must reference authoritative sources, or state that none exist and that we have to deduce the expression's behaviour through empirical evidence only.)}

推荐答案

p>有可能有冲突的相关信息此处，那谈论每个操作数的行的隐含构造，以及关于>行分类比较。

There is potentially conflicting pertinent information here, that talks about the implicit construction of a "row" for each operand, and about row-wise comparison.

它只说 AND 用于排序规则：

行构造函数在其他上下文中是合法的。例如，两个语句之后的
语义上相当：

Row constructors are legal in other contexts. For example, the following two statements are semantically equivalent:

SELECT * FROM t1 WHERE (column1,column2) = (1,1);
SELECT * FROM t1 WHERE column1 = 1 AND column2 = 1;

尽管PostgreSQL 有点更精确：

It goes into no specifics, though PostgreSQL is a bit more precise:

如果所有对应的成员都是
非空且相等，则两行被视为相等;如果任何相应的成员
为非空且不相等，那么这些行是不相等的;否则行比较
的结果是未知（null）。

Two rows are considered equal if all their corresponding members are non-null and equal; the rows are unequal if any corresponding members are non-null and unequal; otherwise the result of the row comparison is unknown (null).

根据MySQL文档的使用示例， code> = 和实证证据使用！= （和阿里尔说，应用程序！（（a = 1）AND（b = 2）...） 适合），我想我们只需要解决上述PostgreSQL引用也适用于MySQL（并提交文档错误！）。

Based on the MySQL documentation examples for usage of =, and empirical evidence for usage of != (and, as Ariel says, the application !((a = 1) AND (b = 2) ...) fits), I think we'll just have to settle for presuming that the above PostgreSQL citation also applies for MySQL (and file a documentation bug!).

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