Figure 1 shows an example of two indexes: one a DPSI and the other an NPSI on the column ZIPCODE.
图1显示了两个索引的一个示例：一个是DPSI，另一个是NPSI，在列z IPCODE上。
2
Because the NPSI is a single ordered list, it is easy to see how DB2 could just toggle back and forth, index to table, index to table, and return rows in ZIPCODE order without sorting.