index key

Indexes do not require that the page free space be tracked , because the point at which to insert a new row is set by the index key values .

Up to 16 columns can be combined into a single composite index key.

A notable exception to this rule is unique indexes where the index key columns do not include the table partitioning key.

The index key of a clustered index cannot contain varchar columns that have existing data in the ROW_OVERFLOW_DATA allocation unit.

Each index key must be unique or contain a NULL in at least one column.

In this case, one of the include columns must be selected for the index key column.

VSAM arranges records by an index key, relative record number, or relative byte addressing.

That means, among other things, getting the order of the key columns right if it's a multi-index key.

None of the rows in the table at time the CREATE INDEX statement is executed can have index key values whose total lengths exceed 900 bytes.

The generated hash value is numeric, and I use this value as single index key for the string being indexed.

Sum the length of each column that will be defined in the index key.

The UNLOAD TABLE statement allows you to unload a table in the order of the index key.

A unique index is one in which no two rows are permitted to have the same index key value.

In a clustered index, the physical order of the rows in the table is the same as the logical (indexed) order of the index key values.

But be careful with this tactic; you do not want to replicate a table in an index by including all of the table's columns in the index key.

Redesign nonclustered indexes with a large index key size so that only columns used for searching and lookups are key columns.

This value is part of the index key and is required to make sure that every row has a unique key value.

Columns; however, such columns cannot be included in the clustered index key.

Searches for duplicates of new index key values in insert and update operations, to enforce PRIMARY KEY and UNIQUE constraints.

It reports only include columns for some queries, so index key columns must be manually selected.

Columns that are not part of the index key can be included in nonclustered indexes.

A column is part of a clustered index key that may be null.

For indexes, the insertion point of a new row is set by the index key.

Put another way, matching starts at the far left of the index key and proceeds rightward.

for a clustered table , the row locator is the clustered index key.

The index key limit might be reduced when you are using VARCHAR or VARGRAPHIC data type.

The query determines whether some columns are part of an index key.

Narrow indexes, or indexes with few columns in the index key, require less disk space and maintenance overhead.

A unique index ensures that the index key contains no duplicate values and therefore every row in the table or view is in some way unique.

The following table summarizes the results of creating indexes that meet or exceed the maximum index key size restrictions.

To calculate the size of an index key, follow these steps.

Key generator function to construct index key during INSERT and UPDATE operations.

neither column of the output result set is a key , but together they form an index key.

The index key size limit also applies to those constraints that are enforced through indexes.

When you create indexes on VARCHAR or VARGRAPHIC columns in your Unicode tables, you need to pay attention of the index key limit.

The LOAD TABLE statement inserts rows into the table in the order of the index key.

It should be noted that the DB2 index key size limit is 1024 bytes, and the index key limit includes all overhead bytes.

This means no two rows can have the same value for the index key.

But, you can perform range scans on the remaining columns in the index key.

IDS now automatically collects index statistics on the leading index key while the index is being created.

For LOAD, all index key sorting takes place simultaneously in the private memory space of one process: db2lrid in SMP, db2lfrm0 in serial.

In this way, you will have all columns needed to cover the query, but the index key itself is small and efficient.

Generally, you should define the clustered index key with as few columns as possible.

Based on the optimizer's estimate, there are eight qualifying RIDs within the target index key range.

If the index key size exceeds 900 bytes, a warning message is displayed.

Returns information about the index key.

In Cheetah (IDS 11), IDS automatically collects index statistics on the leading index key while the index is being created.

In the second table, the index key is being updated when the deadlock occurs.

The maximum size for an index key is 900 bytes.

A clustered index sorts and stores the data rows of the table or view in order based on the clustered index key.

Is the index key column position.

The index key in Node 2 is being updated when the deadlock occurs.

A clustered index sorts and stores the data rows in the table based on the index key values.

The data rows are stored in order based on the clustered index key.

It will be nonnull and 4 bytes in size in rows that have nonunique index key values.

This problem occurs if the column is a clustered index key in Microsoft SQL Server 2000.

SQL Server 2005 retains the 900-byte limit for the maximum total size of all index key columns.

They are not considered by the Database Engine when calculating the number of index key columns or index key size.

These columns are not considered by the Database Engine when calculating the index key size.

Calculating the Size of an Index Key

The CREATE INDEX statement uses the following algorithms to calculate the index key size

MAX of the SUM of the index key column lengths for existing rows

Listing 1. Implementation of the hash index key generator

A 4-byte column that the SQL Server Database Engine automatically adds to a row to make each index key unique.

For an index key column that is of variable length

Specify the number of fixed-length and variable-length columns in the index key and calculate the space that is required for their storage

Bytes in an index key