将SQL query的抽象语法树(AST)转换为SQL算子(operator)树。对于子查询来说,就是将子查询转换为Apply 算子。Apply算子是SQL Server一个算子,APPLY的左表达式:左表达式的每一行都和右表达式进行一次计算,即右表达式需要根据左表达式提供的值进行相关计算来获取相关结果,然后返回给客户端。APPLY的右表达式:是一个子查询或...
StartTime:Time the query began in Coordinated Universal Time (UTC) Duration:Length of time, in milliseconds, that it took to execute the query 下面我们使用日志进行Usage-Based的优化聚合设计 源码下载: begin13 end13 数据库下载 参考资源: 1、SQL Server Analysis Services 官方教程 (http://technet.mi...
Aggregation refers to the collapse of a larger set of rows into a smaller set of rows. Typical aggregate functions are COUNT, MIN, MAX, SUM, and AVG. SQL Server also supports other aggregates such as STDEV and VAR. I’m going to break this topic down into multiple posts. In this post...
CUSTOMER -> Apply -> SELECT,其中 CUSTOMER 作为 Apply 算子的左子树,而 Subuquery 里的语句构造出来的执行计划作为 Apply 的右子树,原先在 SELECT 中的子查询也需要替换成其他等价的 scalar expression,比如当 Apply 是 left outer join 时,IN subquery 就可以替换成对右孩子(代表子查询执行结果)某个字段的 ...
下一版本的 Microsoft SQL Server 将删除该功能。请不要在新的开发工作中使用该功能,并尽快修改当前还在使用该功能的应用程序。 The Aggregation object in Decision Support Objects (DSO) provides access to aggregations associated with a partition in Microsoft® SQL Server™ 2005 Analysis Services. The MD...
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Although precalculation of all possible aggregations in a cube might provide the fastest possible response time for all queries, SQL Server Analysis Services can easily calculate some aggregrated values from other precalculated aggregations. Additionally, calculating all possible aggregations requires signific...
Validate(ValidationErrorCollection, Boolean) Validates the element to which it is appended; returns any errors encountered in a collection. Also contains a parameter to enable return of detailed errors. (繼承自 ModelComponent。) Validate(ValidationErrorCollection, Boolean, ServerEdition) (覆寫 NamedCompon...
PipelineDB allows you to definecontinuous SQL queriesthat perpetually aggregate time-series data and storeonly the aggregate outputin regular, queryable tables. You can think of this concept as extremely high-throughput, incrementally updated materialized views that never need to be manually refreshed. ...
In the worst case, such as the fragment of code above, this is sort of inevitable. The SQL Server 2008 query processor cannot compute aggregates on a stream without destroying the stream. So computing the distinct aggregate consumes the stream, which has to be recomputed for the other ...