"Using Indexes in SQL Server 2008" by Alexander Korotkiy, part 1
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The document provides a comprehensive overview of index architectures in databases, detailing clustered and nonclustered index types, T-SQL commands for creating indexes, and best practices for their use. It outlines when to utilize clustered versus nonclustered indexes based on query characteristics and data attributes, along with options for index configuration. Additionally, it discusses filtered and spatial indexes, emphasizing their application and benefits in optimizing query performance.
![CREATE INDEX (T-SQL)
CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX
index_name
ON <object> ( column [ ASC | DESC ] [ ,...n ] )
[ INCLUDE ( column_name [ ,...n ] ) ]
[ WHERE <filter_predicate> ]
[ WITH ( <relational_index_option> [ ,...n ] ) ]
[ ON { partition_scheme_name ( column_name )
| filegroup_name
| default
}
]
[ FILESTREAM_ON { filestream_filegroup_name |
partition_scheme_name | "NULL" } ]
!
[;]
6](https://image.slidesharecdn.com/using-20indexes-20part-20i-131121081852-phpapp01/85/Using-Indexes-in-SQL-Server-2008-by-Alexander-Korotkiy-part-1-6-320.jpg)
![CREATE INDEX (T-SQL)
<relational_index_option> ::=
{
PAD_INDEX = { ON | OFF }
| FILLFACTOR = fillfactor
| SORT_IN_TEMPDB = { ON | OFF }
| IGNORE_DUP_KEY = { ON | OFF }
| STATISTICS_NORECOMPUTE = { ON | OFF }
| DROP_EXISTING = { ON | OFF }
| ONLINE = { ON | OFF }
| ALLOW_ROW_LOCKS = { ON | OFF }
| ALLOW_PAGE_LOCKS = { ON | OFF }
| MAXDOP = max_degree_of_parallelism
| DATA_COMPRESSION = { NONE | ROW | PAGE}
[ ON PARTITIONS ( { <partition_number_expression> | <range> }
[ , ...n ] ) ]
}
7](https://image.slidesharecdn.com/using-20indexes-20part-20i-131121081852-phpapp01/85/Using-Indexes-in-SQL-Server-2008-by-Alexander-Korotkiy-part-1-7-320.jpg)
![Useful tips
Query in which the
column predicate is
one of these
Exact match to a specific
value
Query description and example
Index to consider
Searches for an exact match in which the query uses the WHERE
Nonclustered or
clause to specify a column entry with a specific value. For example: clustered index on the
Id column.
! Id, [Login], Email FROM Users WHERE Id = 202
SELECT
Searches for an exact match to a value in a specified list of values.
Exact match to a value in an For example:
IN (x,y,z) list
! Id, [Login], Email FROM Users WHERE Id IN (603, 658, 1371)
SELECT
Nonclustered or
clustered index on the
Id column.
Searches for a range of values in which the query specifies any entry
that has a value between two values. For example:
Range of values
! Id, UserId, CreateDate, Content FROM Posts WHERE CreateDate
SELECT
>= '2013-03-01 12:00' AND CreateDate <= '2013-03-01 12:30‘
!
Or
! Id, UserId, CreateDate, Content FROM Posts WHERE CreateDate
SELECT
Clustered or
nonclustered index on
the CreateDate column.
BETWEEN '2013-03-01 12:00' AND '2013-03-01 12:30'
Join between tables
Searches for rows in a table that match a row in another table based
Nonclustered or
on a join predicate. For example:
clustered index on the
Id and UserId columns.
SELECT u.Id, u.[Login], p.Content
!
FROM Users u JOIN Posts p ON u.Id = p.UserId WHERE u.Id = 202
10](https://image.slidesharecdn.com/using-20indexes-20part-20i-131121081852-phpapp01/85/Using-Indexes-in-SQL-Server-2008-by-Alexander-Korotkiy-part-1-10-320.jpg)
![Useful tips
Query in which the
column predicate is
one of these
LIKE comparison
Sorted or aggregated
PRIMARY KEY or UNIQUE
constraint
Query description and example
Searches for matching rows that start with a specific character
string such as 'abc%'. For example:
! Id, [Login], Email FROM Users WHERE [Login] LIKE 'ma%'
SELECT
Nonclustered or
clustered index on the
Login column.
Nonclustered or
Requires an implicit or explicit sort order or an aggregation (GROUP clustered index on the
BY). For example:
sorted or aggregated
column.
SELECT p.Id, p.UserId, u.[Login], p.Content
For sort columns,
FROM Posts p JOIN Users u ON p.UserId = u.Id
consider specifying the
ORDER BY p.UserId, p.CreateDate
ASC or DESC order of
Searches for duplicates of new index key values in insert and update Clustered or
operations, to enforce PRIMARY KEY and UNIQUE constraints. For
nonclustered index on
example:
the column or columns
!
! Users ([Login], [Password], Email)
INSERT
VALUES ('xdfyht', 'dh4G57hn1', 'xdfyht@gmail.com')
UPDATE or DELETE operation Searches for rows in an update or delete operation in which the
in a PRIMARY KEY/FOREIGN column participates in a PRIMARY KEY/FOREIGN KEY relationship,
KEY relationship
with or without the CASCADE option.
Contains one or more columns in the select list that are not used for
searching and lookups. For example:
Column is in the select list
but not in the predicate.
Index to consider
! UserId, CreateDate, Content FROM Posts
SELECT
WHERE UserId = 202 ORDER BY CreateDate DESC
defined in the
constraint.
Nonclustered or
clustered index on the
foreign key column.
Nonclustered index with
Content specified in the
INCLUDE clause.
11](https://image.slidesharecdn.com/using-20indexes-20part-20i-131121081852-phpapp01/85/Using-Indexes-in-SQL-Server-2008-by-Alexander-Korotkiy-part-1-11-320.jpg)
"Using Indexes in SQL Server 2008" by Alexander Korotkiy, part 1
- 1. Using indexes Index architecture clustered nonclustered CREATE INDEX (T-SQL) Useful tips Index options Spatial indexes 1
- 6. CREATE INDEX (T-SQL) CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name ON <object> ( column [ ASC | DESC ] [ ,...n ] ) [ INCLUDE ( column_name [ ,...n ] ) ] [ WHERE <filter_predicate> ] [ WITH ( <relational_index_option> [ ,...n ] ) ] [ ON { partition_scheme_name ( column_name ) | filegroup_name | default } ] [ FILESTREAM_ON { filestream_filegroup_name | partition_scheme_name | "NULL" } ] ! [;] 6
- 7. CREATE INDEX (T-SQL) <relational_index_option> ::= { PAD_INDEX = { ON | OFF } | FILLFACTOR = fillfactor | SORT_IN_TEMPDB = { ON | OFF } | IGNORE_DUP_KEY = { ON | OFF } | STATISTICS_NORECOMPUTE = { ON | OFF } | DROP_EXISTING = { ON | OFF } | ONLINE = { ON | OFF } | ALLOW_ROW_LOCKS = { ON | OFF } | ALLOW_PAGE_LOCKS = { ON | OFF } | MAXDOP = max_degree_of_parallelism | DATA_COMPRESSION = { NONE | ROW | PAGE} [ ON PARTITIONS ( { <partition_number_expression> | <range> } [ , ...n ] ) ] } 7
- 8. Useful tips Consider using a clustered index for queries that do the following: ! • • • • Return a range of values by using operators such as BETWEEN, >, >=, <, and <=. Return large result sets. Use JOIN clauses; typically these are foreign key columns. Use ORDER BY, or GROUP BY clauses. • • • • Are unique or contain many distinct values Are accessed sequentially Defined as IDENTITY because the column is guaranteed to be unique within the table. Used frequently to sort the data retrieved from a table. • • Columns that undergo frequent changes Wide keys ! Consider columns that have one or more of the following attributes: ! ! Clustered indexes are not a good choice for the following attributes: ! 8
- 9. Useful tips Consider the characteristics of the database when designing nonclustered indexes. ! • Databases or tables with low update requirements, but large volumes of data can benefit from many nonclustered indexes to improve query performance. Consider creating filtered indexes for well-defined subsets of data to improve query performance, reduce index storage costs, and reduce index maintenance costs compared with full-table nonclustered indexes. • Online Transaction Processing applications and databases that contain heavily updated tables should avoid over-indexing. Additionally, indexes should be narrow, that is, with as few columns as possible. ! Consider using a nonclustered index for queries that have the following attributes: ! • Use JOIN or GROUP BY clauses. • Queries that do not return large result sets. • Contain columns frequently involved in search conditions of a query, such as WHERE clause, that return exact matches. ! Consider columns that have one or more of these attributes: ! • Cover the query. • Lots of distinct values, such as a combination of last name and first name, if a clustered index is used for other columns. 9
- 10. Useful tips Query in which the column predicate is one of these Exact match to a specific value Query description and example Index to consider Searches for an exact match in which the query uses the WHERE Nonclustered or clause to specify a column entry with a specific value. For example: clustered index on the Id column. ! Id, [Login], Email FROM Users WHERE Id = 202 SELECT Searches for an exact match to a value in a specified list of values. Exact match to a value in an For example: IN (x,y,z) list ! Id, [Login], Email FROM Users WHERE Id IN (603, 658, 1371) SELECT Nonclustered or clustered index on the Id column. Searches for a range of values in which the query specifies any entry that has a value between two values. For example: Range of values ! Id, UserId, CreateDate, Content FROM Posts WHERE CreateDate SELECT >= '2013-03-01 12:00' AND CreateDate <= '2013-03-01 12:30‘ ! Or ! Id, UserId, CreateDate, Content FROM Posts WHERE CreateDate SELECT Clustered or nonclustered index on the CreateDate column. BETWEEN '2013-03-01 12:00' AND '2013-03-01 12:30' Join between tables Searches for rows in a table that match a row in another table based Nonclustered or on a join predicate. For example: clustered index on the Id and UserId columns. SELECT u.Id, u.[Login], p.Content ! FROM Users u JOIN Posts p ON u.Id = p.UserId WHERE u.Id = 202 10
- 11. Useful tips Query in which the column predicate is one of these LIKE comparison Sorted or aggregated PRIMARY KEY or UNIQUE constraint Query description and example Searches for matching rows that start with a specific character string such as 'abc%'. For example: ! Id, [Login], Email FROM Users WHERE [Login] LIKE 'ma%' SELECT Nonclustered or clustered index on the Login column. Nonclustered or Requires an implicit or explicit sort order or an aggregation (GROUP clustered index on the BY). For example: sorted or aggregated column. SELECT p.Id, p.UserId, u.[Login], p.Content For sort columns, FROM Posts p JOIN Users u ON p.UserId = u.Id consider specifying the ORDER BY p.UserId, p.CreateDate ASC or DESC order of Searches for duplicates of new index key values in insert and update Clustered or operations, to enforce PRIMARY KEY and UNIQUE constraints. For nonclustered index on example: the column or columns ! ! Users ([Login], [Password], Email) INSERT VALUES ('xdfyht', 'dh4G57hn1', 'xdfyht@gmail.com') UPDATE or DELETE operation Searches for rows in an update or delete operation in which the in a PRIMARY KEY/FOREIGN column participates in a PRIMARY KEY/FOREIGN KEY relationship, KEY relationship with or without the CASCADE option. Contains one or more columns in the select list that are not used for searching and lookups. For example: Column is in the select list but not in the predicate. Index to consider ! UserId, CreateDate, Content FROM Posts SELECT WHERE UserId = 202 ORDER BY CreateDate DESC defined in the constraint. Nonclustered or clustered index on the foreign key column. Nonclustered index with Content specified in the INCLUDE clause. 11
- 12. Index options (fill factor) 12
- 13. Index options (included columns) 13
- 14. Index options (filtered) Views vs. Filtered Indexes Allowed in expressions Views Filtered indexes Computed columns Yes No Joins Yes No Multiple tables Yes No Simple comparison logic in a predicate Yes Yes Complex logic in a predicate Yes No 14
- 19. Spatial indexes (conditions) • • • • • • • • geometry1.STContains(geometry2) = 1 geometry1.STDistance(geometry2) < @r geometry1.STDistance(geometry2) <= @r geometry1.STEquals(geometry2) = 1 geometry1.STIntersects(geometry2) = 1 geometry1.STOverlaps(geometry2) = 1 geometry1.STTouches(geometry2) = 1 geometry1.STWithin(geometry2) = 1 • • • • geography1.STEquals(geography2) = 1 geography1.STDistance(geography2) < @r geography1.STDistance(geography2) <= @r geography1.STIntersects(geography2) = 1 19