DB 2行压缩功能可以减少磁盘存储需求，同时改进执行全表扫描的大量查询的顺序读取访问。
DB2 row compression features can decrease disk storage requirements while at the same time improve sequential read access of large queries which perform full table scans.
通常来说，您可能只希望获得表中数据的一个子集，因此全表扫描会浪费大量的磁盘I/O，因此也就会浪费大量时间。
Most often, you want only a small subset of the data in the table, so a full table scan wastes a lot of disk I/O and therefore time.
这个报表查询需要该事实表的一个全表扫描。
This report query requires a full table scan of the fact table.
我们发现涉及大量行的查询的性能差异比较大，比如对所有20,000个XML文档进行全表扫描并对每个文档比较字符串。
We found a bigger difference for queries that touch a large number of rows, such as a table scan over all 20,000 XML documents with string comparison on every document.
假设上面示例中的COL1列上有索引，如果对COL1而不是RHS执行类型转换，那么会绕过索引，查询会执行全表扫描。
If you assume that there is an index on COL1 in the above example, if COL1 is type-cast instead of the RHS, then the index will be bypassed and the query will perform a full table scan.
目前，要运行表上的RUNSTATS，就要执行全表扫描。
Currently, a full table scan is performed whenever RUNSTATS on table is run.
清单7中查询的谓词选择性较弱，因此需要对pdbxml表进行全表扫描。
The predicates in the query in Listing 7 are weakly selective so that a full table scan of the PDBXML table is required.
上面的那个查询会执行一个全表扫描，对于一个大表来说这是最慢的一种查询方式。
The preceding query requires MySQL to perform a full table scan, the slowest type of query for a large table.
上面的那个查询会执行一个全表扫描，对于一个大表来说这是最慢的一种查询方式。
The preceding query requires MySQL to perform a full table scan, the slowest type of query for a large table.
应用推荐