When a column is not nullable, ISNULL is not really necessary. So optimizer simplfied the input 'tree'. But the computed column I created continues to use the expression that has ISNULL. So optimizer can't do a match. therefore, it can't use index or statistics on...
This option enables you to create an index on a computed column when Database Engine can't prove with accuracy whether a function that returns computed column expressions, particularly a CLR function that is created in the .NET Framework, is both deterministic and precise.Note You can't create...
When you design an index, consider the following database guidelines:Large numbers of indexes on a table affect the performance of INSERT, UPDATE, DELETE, and MERGE statements because all indexes must be adjusted appropriately as data in the table changes. For example, if a column is used in...
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...
今天本来想对一张数仓表做一个性能优化,方法是通过对一个常用的WHERE条件(COL1 IS NULL OR COLB = 0)创建一个计算列,然后对计算列添加索引从而优化性能。 ALTER TABLE [dbo].[FactTable] ADD COMPCOL_FOR_INDEX_COL3 AS C
ALTER TABLE computed_column_definition은 ALTER TABLE을 사용하여 테이블에 추가되는 계산 열의 속성을 지정합니다.
] type_name REBUILD [ [ NONCLUSTERED ] WITH ( BUCKET_COUNT = bucket_count ) ] } | ADD { <column_definition> | <computed_column_definition> | | | <column_index> } [ ,...n ] | DROP [ { CONSTRAINT [ IF EXISTS ] { constraint_name } [ ,...n ] | INDEX [ IF EXISTS ] ...
ALTER TABLE computed_column_definition especifica las propiedades de una columna calculada que se agrega a una tabla por medio de ALTER TABLE.
column_name AS computed_column_expression [ PERSISTED [ NOT NULL ] ] [ [ CONSTRAINT constraint_name ] { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] [ WITH FILLFACTOR = fillfactor ] [ WITH ( <index_option> [, ...n ] ) ] [ ON { partition_scheme_name ( partition_column_nam...
The insert, upsert, update and delete paths must already know how to run compute expressions for the normal (stored) computed columns. Collaborator petermattis commented Apr 4, 2018 There is also a question of how index selection would utilize an index on a virtual column. For example, if ...