查询优化器不使用此 Density 值,显示此值的目的是为了与SQL Server 2008之前的版本实现向后兼容 Calculated as 1 / distinct values for all values in the first key column of the statistics object, excluding the histogram boundary values. This Density value is not used by the query optimizer and is ...
If preparing for an upgrade to SQL Server or promoting a database compatibility level in any SQL Server platform, considerUpgrading Databases by using the Query Tuning Assistant, which can help compare query performance in two different compatibility levels. ...
查询优化器不使用此 Density 值,显示此值的目的是为了与SQL Server 2008之前的版本实现向后兼容 Calculated as 1 / distinct values for all values in the first key column of the statistics object, excluding the histogram boundary values. This Density value is not used by the query optimizer and is ...
If preparing for an upgrade to SQL Server or promoting a database compatibility level in any SQL Server platform, considerUpgrading Databases by using the Query Tuning Assistant, which can help compare query performance in two different compatibility levels. ...
SQL Server 2014 CE is NOT integrated following the principals of QFEs. This means our expectation is that the new SQL Server 2014 CE will create better plans for many queries, especially complex queries, but will also result in worse plans for some queries than the...
DP_ID_`), KEY `key2` (`NAME_`), CONSTRAINT `a` FOREIGN KEY (`DP_ID_`) REFERENCES `b` (`ID_`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin 1 row in set (0.00 sec) (2)查看业务表SQL执行计划异常时索引 代码语言:javascript 代码运行次数0 运行 AI代码解释 mysql> show...
First published on MSDN on Oct 02, 2015 When we introduced the new CE back in SQL Server 2014, several changes were done regarding the assumptions of the model.
Assume that you have enabledthe new cardinality estimatorin Microsoft SQL Server 2014. When you run a query that contains join statements, you may encounter the following issues: Some queries take significantly longer time to compile, especial...
If you create a new database on SQL Server 2014, compatibility level will be 120. When you upgrade or restore from a previous version to SQL 2014, a user database compatibility level will not be updated. In other words, you will continue to use old cardinality estimator in upgrade and...
SQL Server creates and maintains statistics for temporary tables, which lead to better cardinality estimation and optimal execution plan generation. Table variables have no statistics, which can result in poor cardinality estimation and non-optimal execution plan creation. When you add ...