IFEXISTS(SELECT*FROMsys.tablesWHEREname='computed_column_test_computed')BEGINDROPTABLEdbo.computed_column_test_computedENDIFEXISTS(SELECT*FROMsys.tablesWHEREname='computed_column_test_noncomputed')BEGINDROPTABLEdbo.computed_column_test_noncomputedENDCREATETABLEdbo.computed_column_test_computed ( dttmDATETIME...
Table 'computed_column_test_noncomputed'. Scan count 0, logical reads 100833, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Table 'Numbers'. Scan count 1, logical reads 164, physical reads 0, read-ahead reads 0, lob logical...
where coalesce(column_a, column_b, column_c, column_x) is not null Depending on the cardinality of your data, you may be able to add indexes to help performance. Another possibility is to use persisted computed column that tells you whether all four columns are NULL or not. Share Imp...
A computed column cannot be used as a DEFAULT or FOREIGN KEY constraint definition or with a NOT NULL constraint definition. However, if the computed column value is defined by a deterministic expression and the data type of the result is allowed in index columns, a computed column can be us...
ISqlComputedColumn 类型公开以下成员。方法展开表 名称说明 AddAnnotation 将给定批注添加到此元素。 (继承自 IModelAnnotationHolder。) Delete 从模型中删除此实例。 (继承自 IModelElement。) GetAnnotations() 返回附加到此元素的批注的列表。 (继承自 IModelAnnotationHolder。) GetAnnotations(Type) 返回给定类型...
SQL Server ->> Computed Column(计算列) 2016-04-28 11:33 −... Jerry_Chen 0 4312 SQL Server-聚焦计算列持久化(二十一) 2016-12-15 16:57 −前言 上一节我们结束了Hash Match Aggregate和Stream Aggregate的讲解,本系列我们来讲讲关于SQL Server中的计算列问题,简短的内容,深入的理解,Always to re...
计算列是虚拟列,并非实际存储在表中,除非此列标记为PERSISTED。 计算列的表达式可以使用其他列中的数据来计算其所属列的值。 可以使用 SQL Server Management Studio 或 Transact-SQL 在 SQL Server 中为计算列指定表达式。 限制 计算列不能用作DEFAULT或FOREIGN KEY约束定义,也不能与NOT NULL约束定义一起使用。
I'm trying to create a computed column in order to have a unique index on a nullable column that ignores NULL rows1. I've composed this test case: SELECT TEST_ID, CODE, UNIQUE_CODE, CAST(UNIQUE_CODE AS VARBINARY(4000)) AS HEX FROM ( SELECT TEST_ID, CODE, ISNULL(CODE, CONVERT(...
Msg10609,Level16, State1, Line9Filteredindex'IX_FactTable1_COMPCOL_FOR_INDEX_COL3'cannot be createdontable'dbo.FactTable'because thecolumn'COMPCOL_FOR_INDEX_COL3'inthe filter expressionisa computedcolumn. Rewrite the filter expression so that it doesnotinclude thiscolumn. ...
IFOBJECT_ID('dbo.T1','U')ISNOTNULLDROPTABLEdbo.T1;GOCREATETABLEdbo.T1(column_1AS'Computed column '+column_2,column_2varchar(30)CONSTRAINTdefault_nameDEFAULT('my column default'),column_3rowversion,column_4varchar(40)NULL);GOINSERTINTOT1DEFAULTVALUES; ...