Note If multiple table operators appear in the FROM clause, they are processed from left to
right. The result of each table operator is provided as the left input to the next table operator.
The fi nal virtual table will be used as the input for the next step.
Caution Because the data is not yet grouped, you cannot use aggregates here—for example, you
cannot write WHERE orderdate = MAX(orderdate). Also, you cannot refer to column aliases created
by the SELECT list because the SELECT list was not processed yet—for example, you cannot write
SELECT YEAR(orderdate) AS orderyear . . . WHERE orderyear > 2008.
aggregate [ˈægrigeit]
n.总数，合计 a.合计的 vt.合计；聚集
