[求助]sybase执行计划索引问题求助。

randy546

免费乐捐，感谢支持

使用执行计划查看的时候其中2张表的使用情况如下：

其中一张表的索引使用情况是：       

        Positioning at index start.
        Index contains all needed columns. Base table will not be read.

而另一张表的使用情况是：

        Positioning by key.
        Keys are:
            custid  ASC

请问下是不是上面的Positioning at index start.是没有用到索引的？还是什么情况啊？执行的时候效率很低！

谢谢了！

FROM TABLE
            tc_servbaseinfo
            b
        Nested iteration.
        Index : XIE7tc_servbaseinfo
        Forward scan.
        Positioning at index start.
        Index contains all needed columns. Base table will not be read.
        Using I/O Size 16 Kbytes for index leaf pages.
        With LRU Buffer Replacement Strategy for index leaf pages.

        FROM TABLE
            tc_custbaseinfo
            c
        Nested iteration.
        Using Clustered Index.
        Index : tc_custbas_17405822582
        Forward scan.
        Positioning by key.
        Keys are:
            custid  ASC
        Executed in parallel with a 4-way hash scan.
        Using I/O Size 2 Kbytes for index leaf pages.
        With LRU Buffer Replacement Strategy for index leaf pages.
        Using I/O Size 2 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

randy546

没人知道指点下买？？

songsh

不是没用到索引， 而是上面的用的索引不合理 所以才效率低

lovelyni

来顶一下