了解使用各种 JOIN 运算访问来自多个表的数据的 T-SQL 查询。 学习目标 完成本模块后,你将能够: 描述联接概念和语法 编写使用内部联接和外部联接的查询 编写使用交叉联接的查询 编写使用自联接的查询 开始 添加 添加到集合 添加到计划 添加到挑战 先决条件 ...
Instructs the Query Optimizer to use the average selectivity of the predicate across all column values, instead of using the runtime parameter value when the query is compiled and optimized. If you use OPTIMIZE FOR @variable_name = <literal_constant> and OPTIMIZE FOR UNKNOWN in the...
Instructs the Query Optimizer to use the average selectivity of the predicate across all column values, instead of using the runtime parameter value when the query is compiled and optimized. If you useOPTIMIZE FOR @variable_name ...
Not all features that vary by compatibility level are supported on Azure SQL Database. Find current compatibility level To determine the current compatibility level, query thecompatibility_levelcolumn ofsys.databases. SQL SELECT[name], compatibility_levelFROMsys.databases; ...
By default,ROWS_PER_BATCHis unknown. SpecifyingROWS_PER_BATCH = 0is the same as omittingROWS_PER_BATCH. ORDER ( {column[ ASC | DESC ] } [ ,...n] [ UNIQUE ] ) An optional hint that specifies how the data in the data file is sorted. By default, the bulk operation assumes the da...
• Try to query only INFORMATION_SCHEMA tables that are views on data dictionary tables. • Try to query only for static metadata【ˈmetədeɪtə】. Selecting columns or using retrieval conditions for dynamic metadata along with static metadata adds overhead to process the dynamic metad...
For this method to work, it is sufficient that there be a constant equality condition for all columns in a query referring to parts of the key coming before or in between parts of the GROUP BY key. The constants from the equality conditions fill in any “gaps” in the search keys so ...
On account of the variable number of versions, we can use some dynamic SQL to generate and execute the query. DECLARE @Piv NVARCHAR( MAX ), @Col NVARCHAR( MAX ), @SQL NVARCHAR( MAX ); SELECT @Piv = LEFT( b.Piv, LEN( b.Piv ) - 1 ) FROM ( SELECT N'[' + CONVERT( VARCHAR( ...
<order_clause> ::= { <column_name_in_clr_table_type_definition> [ ASC | DESC ] } [ , ...n ] <method_specifier> ::= assembly_name.class_name.method_name <clr_function_option> ::= { [ RETURNS NULL ON NULL INPUT | CALLED ON NULL INPUT ] | [ EXECUTE_AS_Clause ] } <clr_ta...
This latter calculated column is identical – in structure – to the ranking in the previous example. Because it uses the Name Ranked column, the algorithm is the same: it is ranking two numbers. Dynamic ranking on Rounded Sales and customer code If you need a dynamic ranking, then you nee...