SQLServer执行计划成本(续1)
- WBOYOriginal
- 2016-06-07 17:46:571178browse
聚合
查询里使用聚合函数(MIN、MAX、COUNT、AVG或SUM)时发生流聚合(Stream Aggregate)和标量计算(Compute Scalar)如下所示。
SELECT COUNT(*), AVG(Value) FROM M2C_10
MIN和MAX函数要求流聚合操作。在执行计划里其他的函数要求流聚合后跟一个或多个标量计算操作。
图2-12.流聚合和标量计算的执行计划
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