但是，如果使用任意数量的表和字段动态地指定from子句或result子句，就不能这样了，因为在编程时无法确定结果集类型。
This no longer works if you use arbitrary tables and fields to specify the from clause or the result clause dynamically, though, because the result set types cannot be determined at programming time.
这样的结果集可以看作是“视图”，它们不是显式地在数据库中创建的，而是由存储过程动态地创建的。
Such result sets can be regarded as "views" that are not explicitly created in the database but are created on the fly by the stored procedure.
MQT是通过select语句定义的(通常是一个结果集)，这样就不需要在执行查询时动态地构建这个结果集。
An MQT is defined by way of a SELECT statement-usually a result set that would otherwise have to be dynamically built when a query executes. Here are three great things about an MQT.
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