该查询计划显示了一个全表扫描。
该查询计划显示了全表扫描。
索引能够避免全表扫描，从而能够提高查询性能。
Indexes improve query performance by avoiding a full table scan.
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.
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.
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.
如果没有为ucname创建索引，DBMS仍然执行全表扫描，但是不会对数据进行进一步处理来判断其是否满足查询。
If there is no index on ucname, the DBMS still does a full table scan, but it need not do any further processing on the data to determine whether or not it satisfies the query.
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.
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.
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.
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