为什么我们必须在“全部插入"之后进行选择? [英] Why do we have to make a SELECT after an 'INSERT ALL'?

问题描述

正如我在许多站点上看到的那样，如果要创建INSERT ALL，则必须以SELECT (Like SELECT * FROM dual;)

As I seen on many sites, if I want to make an INSERT ALL, I have to finish it with a SELECT (Like SELECT * FROM dual;)

为什么?

推荐答案

根据INSERT ALL的语法，子查询是必需的(请参阅

A subquery is mandatory per the syntax of INSERT ALL (see http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_9014.htm#i2111652)

对于子查询返回的每一行(即SELECT语句)执行insert子句. SELECT * FROM dual返回单个行，因此insert_clause(s)仅执行一次(当您要插入一组硬编码的值时，这很有用)

the insert clause is executed for each row returned by the subquery (i.e. the SELECT statement). SELECT * FROM dual returns a single row, so the insert_clause(s) is executed once (which is useful when you want to insert a hardcoded set of values)

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