基本上，它会权衡使用索引来遍历选择的行或者对表进行扫描这两种方式。
Basically, it's weighing the choice of using the index to walk through the selected rows or doing a table scan.
初级的方法是使用一个游标对表进行扫描，并为每一行执行一个定位的更新语句。
The naive approach USES a cursor to scan the table and execute a positioned update statement for each row.
用行扫描的方法进行车牌的上下边界定位。
The row scan method is utilized to locate the up and down edges of the plate.
本文定量地分析了行扫描仪的目标分辨能力。
The target resolution of line scanners is analyzed quantitatively.
后者利用前一行扫描高度数据作为当前行z向扫描器驱动的参考输入。
The latter USES the last line height signal as the reference input of Z-control in the current line scan.
针对车牌区域内字符串具有丰富的纹理特征，本文提出了一种基于行扫描的车牌定位算法。
An algorithm of license plate location based on line scanning is proposed according to the abundant texture features in the domain of vehicle license plate.
建立了TDICCD交汇测量系统中CCD行扫描速率和目标运动速率同步控制的数学模型。
The math model about synchronism controlling between line scanning rate of CCD and object moving speed in the TDI CCD intersection measuring system is established.
在激光照排机中，成像激光光点的坐标是由水平方向的行扫描和垂直方向的场扫描的同步运动决定的。
In the laser typesetter, the coordinates of the imaging laser points are determined by synchronous movement of row and column scanning motors.
HD具有与其前一代，即LSP红外线行扫描仪完全相同的外形，所以它与所有现存的安装硬件兼容。
The LSP-HD has an identical form factor to its predecessor, the LSP Infrared Linescanner, so compatibility with all existing mounting hardware is maintained.
用非接触型镜面反射显微镜对100名正常人角膜内皮行扫描检查；中央内皮黑区的发现率为16％。
The corneal endothelium of 100 normal subjects was examined by scanning with the noncontact clinical specular microscope.
高压硅堆是彩电和彩色显示器行输出电路中的关键器件，其开关速度的快慢直接限制了行扫描频率的高低。
High voltage silicon pile is the key component of the output circuits of color TV and color monitor, whose switch frequency is the direct restrictive factor of line scan.
该模型综合考虑了目标长度、目标运动速率、TDICCD行扫描速率、成像系统放大倍数、TDI CCD像元尺寸等因素。
This model synthetically considers length and velocity of target object, line scanning rate of TDI CCD, magnifying power of imaging system, size of pixel, and so on.
介绍了在电视接收机、显示器行扫描电路中的磁饱和电抗元件(行线性校正线圈)的原理及对铁氧体磁芯材料性能和工艺的要求。
This article describes the principium of line scan revise winding used in the line scan circuit of TV receiver and display, and the requirement for the characteristics of the ferrite core.
在我们的例子中，通过索引扫描得到6574个候选行。
在这里，使用一个表扫描来访问行是更好的选择。
Accessing the rows using a table scan is a better choice in this case.
但是如果某个表有100,000或更多的行，那么重复的连续扫描将对性能产生致命影响。
But if a table has 100,000 or more rows, repeated sequential scans are deadly to performance.
DB 2可以使用关系索引和xml索引来快速检索所关注的数据，避免了盲目地扫描表中的所有行。
DB2 can use both the relational and XML indexes to quickly pinpoint the data of interest, avoiding a costly scan of all rows in the table.
Time维度表中满足过滤条件的 time_id连接键被散列以创建一个位向量，用于过滤以上跳跃式扫描的Orders 表行。
The time_id join keys that meet the filter requirements on the Time dimension table are hashed to create a bit vector that filters rows of the Orders table from the skip scan above.
接下来，参赛者需要向每个表添加合适的索引，以便Informix无需扫描整个表即可找到它需要更新的行。
Next, contestants needed to add appropriate indexes to each table, so that Informix would not scan the whole table to find the row it needed to update.
对于所扫描的数据包内的所有行，使用协议级别作为前缀。
Each line is prefixed with the protocol level within the packet that was scanned.
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.
不管数据行是否被提交，以及根据语句的谓词它是否被排除，对于索引扫描和表访问都执行这样的锁定操作。
This locking was done for both index scans and table access whether or not the row of data was committed or whether it would have been excluded based on the statement's predicates.
如果查询中的表极其小(通常少于1,000行)或者是群集表，而且查询根本没有选择性的话，那么使用表扫描会更好一些。
If the table in your query are pretty small (usually fewer than 1,000 rows) or clustered tables, and your query is not selective at all, it would be beneficial to use a table scan.
一般来说，索引扫描是访问数据的最有效的方法，尤其是表很大但符合条件的行很少的时候。
Index scans are usually the most efficient way to access data, especially when the table is large but the number of qualified rows is small.
如果没有索引满足所取的行的要求顺序，或者优化器断定排序的代价低于索引扫描，那么就需要进行排序。
Sorting is required when no index satisfies the requested ordering of fetched rows, or the optimizer determines that a sort is less expensive than an index scan.
对于所扫描的每一行记录，FETCH(3)都会读取t2的status字段。
For each of rows being scanned, FETCH (3) will read the status column from T2.
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.
其他压缩技术只在每行的一部分中寻找重复模式，而StorageOptimization会扫描整个行，无论行中有多少列。
Unlike other compression techniques that scan only a portion of each row for repeating patterns, Storage Optimization scans the entire row, regardless of how many columns it intersects.
其他压缩技术只在每行的一部分中寻找重复模式，而StorageOptimization会扫描整个行，无论行中有多少列。
Unlike other compression techniques that scan only a portion of each row for repeating patterns, Storage Optimization scans the entire row, regardless of how many columns it intersects.
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