you've requested rows directly in the query that's why you got a clustered index SEEK . Clustered index scan:When Sql server reads through for the Row(s) from top to bottom in the clustered index. for example searching data in non key column. In our table NAME is non key column so ...
analysis: SET STATISTICS IO ON -- Turn Graphical Showplan ON (Ctrl+K) -- First, a point query (also, see how a bookmark lookup looks in 2005) SELECT * FROM ChargeHeap WHERE Charge_no = 12345 go SELECT * FROM ChargeCL WHERE Charge_no = 12345 go -- What if our query is less ...
When you create a UNIQUE constraint, a unique nonclustered index is created to enforce a UNIQUE constraint by default. You can specify a unique clustered index if a clustered index on the table doesn't already exist. An index created as part of the constraint is automatically given the same...
如果沒有可為 Null 的索引鍵資料行,請將 Index_Null_Bitmap 設成0。 計算可變長度的資料大小: 如果在索引鍵中有可變長度的資料行,包含任何所需的叢集索引鍵資料行,請決定在索引資料列中儲存資料行所需的空間。 Variable_Key_Size = 2 + (Num_Variable_Key_Cols x 2) + Max_Var_Key_Size 加入Max_Var_...
When a clustered index structure is created, disk space for both the old (source) and new (target) structures is required in their respective files and filegroups. The old structure isn't deallocated until the complete transaction commits. Additional temporary disk space for sorting might also b...
When you create a UNIQUE constraint, a unique nonclustered index is created to enforce a UNIQUE constraint by default. You can specify a unique clustered index if a clustered index on the table doesn't already exist. An index created as part of the constraint is automatically given the same...
SQL Azure tables must contain a clustered index. Non-clustered indices can be subsequently created on selected tables. You can create spatial indices, but you cannot create XML indices. Heap tables are not supported. CLR geo-spatial types (such as Geography and Geometry) are supported, as is ...
Database maintenance can cause downtime if an operation is performed that needs to place a lock on a table for an extended period of time. Examples of such operations include: Creating or rebuilding a nonclustered index (can prevent table modifications) ...
Database maintenance can cause downtime if an operation is performed that needs to place a lock on a table for an extended period of time. Examples of such operations include: Creating or rebuilding a nonclustered index (can prevent table modifications) ...
With a clustered index the physical (on disk) order and the logical order of the data in a table are the same. Every time you edit/change order of the rows they are rearranged on disk. With unclustered index the data refers to another table that contains pointers to the ...