然而，对于表扫描，块锁不会推迟。
该查询计划显示了全表扫描。
使用分区修剪的表扫描(TBSCAN)。
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.
还是如图11所示，每次执行查询都有两个表扫描。
Also as shown in Figure 11, you can see that there are still two table scans for each execution of the query.
这将允许下面两个查询来使用索引访问，而不是表扫描。
This will allow both of the following queries to use indexed access rather than table scans.
行读取的数目（77）表明很可能发生表扫描。
The number of rows read (7700000) versus the number of rows written (77) show that a table scan is likely happening.
这比不使用任何索引的两个表扫描的嵌套循环连接要快得多。
This is a lot faster than a nested loop join of two table scans without any index usage.
执行索引分析，确保索引正确，从而能避免不必要的表扫描。
Perform index analysis to make sure that the right indexes exist to help avoid unnecessary table scans.
通过索引扫描还是表扫描来访问外部表则取决于该表。
The outer table can be accessed by an index scan or by a table scan, depending on the table.
可以从WHERE子句中提取确定性函数调用，避免不必要的表扫描。
Deterministic function calls can be extracted from the WHERE clause to avoid unnecessary table scan.
在缺少当前统计的情况下，优化器选择对参与联接的两个表进行表扫描。
The optimizer, in the absence of current statistics, is choosing to do a table scan on both tables involved in the join.
物理数据或键的连续性对于表扫描或键-索引扫描的速度十分重要。
Contiguity of physical data or keys is important to the speed of table scans or key-index scans.
该例中，表扫描极其昂贵，因为Informix引擎必须随机地访问数据。
In this case, a table scan is very expensive, because the Informix engine has to access data randomly.
因此，DB 2不能使用那些索引，而是会采取表扫描来确保正确的查询结果。
Thus, DB2 cannot use those indexes and resorts to a table scan to ensure a correct query result.
分段和PD Q优先级也对于数据的检索速度有极大的影响，并有助于表扫描。
Fragmentation and PDQ priority also have a huge effect on the speed of data retrieval and will help table scans.
如果该值很大，表示可以通过对谓词列创建索引来避免多余的表扫描。
A high value here can indicate excessive table scans that can be prevented by creating indexes on the predicate columns.
这使得DB 2查询使用表扫描代替索引扫描，并降低了数据库的性能。
This makes DB2 queries use table scans instead of index scans and degrades database performance.
该计划展示了aggregate_salesMQT上的一个表扫描。
The plan shows a table scan over the aggregate_sales MQT. Moreover, the details of the operator table scan shows the following details.
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.
报告的表扫描次数表示在下午 1点到 2点之间在这个表上执行的扫描。
The number of table scans reported represents the scans on the table between 1:00 p.m. and 2:00 p.m.
收集不依赖于连接(JOIN)的基本访问(表的索引扫描和表扫描)的计数。
Gather counts for base accesses (an index scan or a table scan of a table) that are not dependent on a join.
由于INSERT和select语句之间没有COMMIT，死锁可能是由表扫描引起的。
Since there is no COMMIT between the INSERT and SELECT statement, potentially the deadlock is caused by a table scan.
因为该select语句的结果集中只期望一行，所以表扫描在这里被认为是代价较高的操作。
Since only one row is expected in the result set from this SELECT statement, the table scan here is considered an expensive operation.
最简单的方法是连续读取表中的数据，就是按照我们通常调用它的方法来执行表扫描。
The simplest way is to read the table's data sequentially, performing a table scan as we usually call it.
因此，在决定选择哪种联接方法时，优化器为内部表扫描平衡排序成本和性能优势以便促进决策。
Therefore, when deciding which join method to choose, the optimizer balances the sort cost and the performance benefit for the inner table scan to drive the decision.
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.
表2总结了此次表扫描的性能如何能从我们的两个设计决策中受益：原子站点分离和压缩。
Table 2 summarizes how the performance of this table scan query has benefited from two of our design decisions: atom site separation and compression.
如果没有创建合适的索引，或者如果索引扫描的成本更高一些，优化器通常就选择表扫描。
The optimizer normally chooses a table scan if no appropriate index has been created or if an index scan would be more costly.
如果表中的数据进行了群集化处理，或者是有物理次序的，那么表扫描的成本就可能相当低。
The costs of table scans can be fairly low if the data in the table is clustered or if it is in physical order.
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