1 Applies to SQL Server 2012 (11.x) and later versions, and Azure SQL Database.2 Applies to SQL Server 2017 (14.x) and later versions, and Azure SQL DatabaseIf ALL is specified with PARTITION = <partition_number>, all indexes must be aligned. This means that they're partitioned ...
1 Applies to SQL Server 2012 (11.x) and later versions, and Azure SQL Database.2 Applies to SQL Server 2017 (14.x) and later versions, and Azure SQL DatabaseIf ALL is specified with PARTITION = <partition_number>, all indexes must be aligned. This means that they're partitioned ...
The maximum number of values per record for a multi-valued index is determined by the amount of data than can be stored on a single undo log page, which is 65221 bytes (64K minus 315 bytes for overhead), which means that the maximum total length of key values is also 65221 bytes. Th...
This means that the columns returned by either the SELECT clause and all the WHERE and JOIN arguments are covered by the index. There's potentially much less I/O to execute the query, if the index is narrow enough when compared to the rows and columns in the table itself, mean...
deterministic. Use theIsPreciseproperty of the COLUMNPROPERTY function to determine if a deterministic column in a view with schema binding is precise. COLUMNPROPERTY returns 1 if TRUE, 0 if FALSE, and NULL for input that is not valid. This means the column is not deterministic or not precise...
最近用explain命令分析查询sql执行计划,时而能看到Extra中显示为"Using index"或者"Using where; Using Index",对这两者之间的明确区别产生了一些疑惑,于是通过网上搜索、自行实验探究了一番其具体区别。 测试数据准备 以下表作为测试表进行sql分析。 CREATE TABLE `test_table`(`id` bigint(20)unsigned NOTNULLA...
This means they may be selected by the query optimizer and, if necessary, specified in index hints. Target The target or targets is the new index (or heap) or a set of new indexes that is being created or rebuilt. User insert, update, and delete operations to the source are applied ...
For example, suppose an application frequently queries thelast_name,job_id, andsalarycolumns in theemployeestable. Also assume thatlast_namehas highcardinality, which means that the number of distinct values is large compared to the number of table rows. You create an index with the following co...
In this context, highest means highest in the sorting sequences of the index columns. In a column defined as ascending (ASC), highest and lowest have their usual meanings. In a column defined as descending (DESC), the lowest actual value is highest in the sorting sequence. If you use ...
It is syntactically valid to omitindex_listforUSE INDEX, which means“use no indexes.”Omittingindex_listforFORCE INDEXorIGNORE INDEXis a syntax error. You can specify the scope of an index hint by adding aFORclause to the hint. This provides more fine-grained control over optimizer selection...