Questions tagged [nonclustered-index]
The nonclustered-index tag should be used for questions regarding how to implement and troubleshoot supplemental indexes used primarily to enhance performance. The term nonclustered is typically a SQL Server-specific term.
181
questions
5
votes
2answers
518 views
With a multi column non clustered index, and the SELECT on middle column, why does SQL server query this index rather than scanning the table?
A single non clustered is set up on LastName, FirstName, MiddleName - in that order.
SELECT * FROM PERSON
WHERE FirstName='xyz'
Why does the execution plan use the index and not scan the table ...
1
vote
1answer
316 views
Why engine choose Index Scan instead of Index Seek for Group By query?
I have query:
SELECT
M_nvarchar_3
, MA_nvarchar_40
, W_nvarchar_4
, LB_nvarchar_2
, SUM(ST_decimal_13_3)
, SUM(CW_decimal_13_3)
...
0
votes
0answers
44 views
Working with index-key sizes which are close to the DBMS's index-key size limit
I might need to work with relatively large (non-clustered) index keys (between 1KB to 4KB). I found that Spanner and DB2 support 8KB index-key size, MSSQL allows 1.7KB and Postgress around 2.6KB (1/3 ...
0
votes
2answers
68 views
What are the more important columns to include in NONCLUSTERED INDEX - from Group by or Where?
I am thinking about adding a NONCLUSTERED INDEX to a table in SQL Server 2016. I found that most queries refers to WHERE clause like:
WHERE varcharColumn <> ''
and varcharColumn2 = '2'
and ...
0
votes
2answers
53 views
Is it worth to use NONCLUSTERD FILTERED INDEX with clause `<>''`?
I am just thinking to create NONCLUSTERED FILTERED INDEX with condition:
WHERE varcharColumn <> ''
This columns contains around 3127 different values including value ''. All the queries has ...
-1
votes
0answers
30 views
How does sql server decide when to stop after starting to read an index?
Let's say the sqls server is reading an index. It may be clustered or non clustered index.
Say the index has values from 1 to 999999. And assume sql server decides to read the index.
When the where ...
1
vote
0answers
61 views
How to estimate the nonclustered index size before its creation?
I created two scenarios and expected to see the same result but the results were noticeably different. I would like to know where I did wrong.
Scenario 1
Create table mytable1 with clustered index and ...
0
votes
2answers
40 views
Index Drop for Partial Overlap?
I'm working with a 50mil row table with the following:
Clustered Index keyed on [Col1]
Nonclustered Index keyed on [Col1], [Col2] (no includes)
It seems like the right call here would be to drop #2 ...
0
votes
1answer
80 views
Optimizer Not using Non Clustered Column Store Index for Update / Delete Statements
My Table tbl_FieldeData_ColStore Data Example:
/NonClustred Column Store Index on Table/
CREATE NONCLUSTERED COLUMNSTORE INDEX NCCI ON tbl_FieldeData_ColStore
(
PDID,FieldID
)
/Below Select was ...
-2
votes
1answer
46 views
Will index on a partition that doesn't include partition column work fast?
Let's say I have a huge table with columns [CloseOfBusinessDate], [DataSourceID], etc.
[CloseOfBusinessDate] is a partition column and I have a clustered index on that column (on ...
0
votes
0answers
30 views
Searching text using LIKE, and Included Column
SELECT * FROM Table WHERE (Column1 = 'ED69K')
SELECT * FROM Table WHERE (Column1 LIKE '% ED69K%')
I have a wide table with 25 columns on the table. The above queries do need to do key lookup ...
0
votes
1answer
70 views
Should I rebuild index in non clustered index?
I'll be rebuilding our index in SQL Server since our fragmentation rate on all indexes for all tables are so high. Should I include to rebuild my non-clustered index also? Or rebuilding of clustered ...
0
votes
0answers
36 views
Rebuild indexes makes switch partitions useless (SQL Server)
I have a big table containing multiple indicators per ticker. The table is partitioned by indicator. Each indicator has nearly 50 million rows and currently there are about 30 indicators and they will ...
0
votes
0answers
43 views
SQL2005 Index exists in sys.indexes but not on table
I have a routine that runs through all the non-clustered indexes in a given database on SQL2005 (SP3), and reorganizes and rebuilds them (if fragmentation > 20%). This process is erroring out on ...
0
votes
1answer
34 views
Is there a performance difference between a Dropped Index and a Disabled Index, for a NON-Clustered Index
I'm aware that there are substantial differences between Dropping and Disabling a CLUSTERED Index, but I want to know about NON-CLUSTERED indexes.
And I'm aware that Disabling an Index retains the ...
0
votes
0answers
25 views
Non cluster indexing with combination or on single entity for multiple columns
I am new to db design I also read concepts of non cluster indexing and know about the combined non cluster indexing but in my scenario I am having user table with multiple search on column
table ...
0
votes
0answers
52 views
Update query performance improvement (MS-SQL)
UPDATE M SET ARCHIVE_FLAG = 'N' FROM MARKPOSTED_TMP M WHERE
EXISTS (SELECT 1 FROM SHFMKPSTMM S INNER JOIN SHIFT_TMP S1
ON M.MARKID = S.MARKID AND
S.SHIFTID = S1.SHIFTID AND S1.ARCHIVE_FLAG <> '...
0
votes
3answers
117 views
Space consumed by a column in non clustered index
I m planning to add a key column index in one of the existing non clustered index in a big table which have millions of rows rather than create a new non clustered index. Is that any way for me to ...
0
votes
1answer
68 views
What should be the size of nonclustered index?
I was experimenting with nonclustered indexes, especially their sizes. My aim was to understand how the amount of index keys in Clustered index affects the final size of Nonclustered index. I ...
0
votes
2answers
36 views
SQL Server - Overlapping NC Indexes, Drop Question
I'm doing some index cleanup/tuning on a SQL '14 DB and ran across a 6MM row, 16 field table with a sound-looking clustered index and two nonclustered, non-unique indexes having the following ...
1
vote
3answers
63 views
SQL Server - Unique Constraint Syntax
Is there a functional difference between the tables built in the following two ways?
CREATE TABLE [dbo].[test_uq](
[ID] [int] NOT NULL,
[f1] [int] NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[...
0
votes
1answer
25 views
SQL 2016 - NU/NC Index Missing From sys.partitions
Is there a reason that a non-unique, non-clustered index would have 0 corresponding records in the sys.partitions view? There is a CI on the same table and there is a record for it in the view. My ...
0
votes
4answers
84 views
Is a Non-Clustered index needed when referencing a small table with a Foreign Key
I'm not a DBA, excuse me if this question sounds dumb. Hope I can get help from an experienced DBA, because I'm questioning this for a long time.
Assume there are 2 tables, one table with a lot of ...
0
votes
0answers
12 views
How to avoid duplicate in mysql INNODB transaction for non index key?
I have a INNODB table with txnno column without unique index but I have primary key on another column. Now I am inserting transaction from multiple places. And there are some concurrent insertion ...
1
vote
2answers
95 views
Index with few seeks and many updates [closed]
Say I create a nonclustered index on a table. After a week I look at the sats, e.g. number of seeks, scans, updates etc. E.g. say I have 10 seeks and 10000 updates. How can I measure the cost of the ...
1
vote
2answers
102 views
How to reduce fragmentation of nonclustered index on date partitioned log table
Looking for some advice before I follow my gut on this and rebuild the nonclustered index to lead with our partition key. This is an insert-only table which is never updated or deleted, we keep a ...
0
votes
2answers
42 views
Key Lookup isn't applied by default?
I'm trying to learn about covering indexes. In the Northwind database, I select from the table Categories:
As you can see the table has a non-clustered index on the column CategoryName.
This SQL ...
1
vote
1answer
207 views
Select Query slow for Non-clustered index
I am using SQL Server 2008 R2. Select query is slow when non cluster index is used in the table compared to table without index.
Query Used:
select * from table order by customer_name
It is too ...
1
vote
1answer
135 views
Facing deadlock after introducing a new Non-clustered Index on Heap
I am facing a strange issue wherein I had analyzed a stored procedure which runs every 3 minutes and was putting load on CPU. I found out that there are number of select statements which is part of ...
0
votes
4answers
176 views
Using an index when leading column is not in the predicate
Are there any circumstances when an index could be used when not all the index columns are included in the predicate? In my case the leading column in the index is unique and is part of the unique ...
1
vote
1answer
62 views
Non-clustered index with WHERE clause
I have a large table (around 100 million rows). I am trying to optimize searches. Most of my searches use two columns: bar nvarchar(64) and foo nvarchar(64).
I am only interested in foo when:
foo = '...
1
vote
1answer
141 views
Why does my execution plan show a Clustered Index Scan is occurring when using an index hint that specifically uses a Nonclustered Index?
The Backstory:
I have a table with the following structure:
CREATE TABLE WideTable1
(
BoringColumn1,
BoringColumn2,
CellPhoneNumberColumn Phone(VARCHAR(20)), -- User-defined types, see ...
0
votes
2answers
85 views
What does it mean that a "clustered index does not store pointers to the data"? [duplicate]
I am a beginner in SQL and Database Administration and I am trying to undestand the difference between clustered and non-clustered indexes. More or less I understood what the different tasks are but I ...
2
votes
2answers
146 views
SQL Server Index Scan when using 'OR' operator
We implemented a Google-style search where SQL queries are run after a debounce is triggered from the front-end. (We know SQL is probably the wrong technology for this, but I'm knee-deep in startup-...
1
vote
1answer
103 views
Nonclustered Index Rebuild Online on Heap Table
Recently read that rebuilding a heap online in SQL Server Enterprise is single threaded and does not go parallel.
My question is: If you try to rebuild online just non-clustered indexes on a heap ...
0
votes
1answer
95 views
MySQL Clustered Index or Non Clustered index? (Database Design)
I know this might be a basic thing for you guys in this corner of SE but I'm having some trouble figuring out the best option for designing my DB.
I am creating a custom app where the user will be ...
5
votes
1answer
277 views
Can adding a columnstore index to a table affect read performance of a query that uses a rowstore index on the same table?
I'm doing some testing of columnstore indexing on a single table that has about 500 million rows.
The performance gains on aggregate queries have been awesome (a query that previously took about 2 ...
0
votes
0answers
30 views
MySQL InnoDB Weird Query Performance
I designed two tables, both using InnoDB.
The first one has columns "Offset, Size, and ColumnToBeIndexed" with BIGINT "Offset" being the primary key, and the second one has columns "OffsetAndSize, ...
1
vote
0answers
23 views
How to create Non-clustered Covering index on PK while creating a table
I am trying to create a table where PK will not be a clustered index. PK will be non clustered with INCLUDE clause to add cover.
CREATE TABLE [Ref].[User](
[UserRegisteredId] [varchar](100) NOT ...
0
votes
1answer
71 views
difference between create constraint non clustered and create index non clustered
I am new to sql server. i was trying to learn creating index. i tried to create a table with below query:
CREATE TABLE [Ref].[Country](
[CountryId] [uniqueidentifier] NOT NULL,
[CountryName] ...
0
votes
1answer
64 views
Value of the Included Column is stored in Leaf Node?
There is SQL- script, which generated the Nonclustered Index with Included Column:
CREATE TABLE users
(
id INT,
firstname VARCHAR(50),
surname VARCHAR(50)
);
CREATE ...
0
votes
1answer
63 views
Why scan clustered index instead seek nonclustered index?
There is SQL script:
CREATE TABLE users
(
id INT,
firstname VARCHAR(50),
surname VARCHAR(50)
);
CREATE CLUSTERED INDEX ix_users_id
ON users (id);
CREATE ...
0
votes
1answer
47 views
If PK is Non-Clustered index, how to identify clustered index candidate?
I'm designing a database for insurance company. I want to make Primary key as GUID-uniqueidentifier. I want to create Index for each table in database for performance optimization.
I did research ...
1
vote
1answer
108 views
Results in sys.dm_db_index_usage_stats
I have this query below that I use to clean up indexes that are not being used anymore to reduce runtime and overhead during index maintenance and during inserts. On some tables that I've ran this ...
-1
votes
1answer
157 views
How many non-clustered indexes on one table? [closed]
I have a table with 12 indexes with just one column which are added by EF automatically:
CREATE NONCLUSTERED INDEX [IX_Table_Col1] ON [dbo].[Table]([ColId1] ASC) WITH (STATISTICS_NORECOMPUTE = OFF, ...
2
votes
3answers
477 views
Is it possible to track the progress of when I drop a the primary key clustered index on a table?
I have a large primary key clustered index I need to drop. I believe dropping it will also trigger index rebuilds on the nonclustered indexes (which are also pretty big). Is there a way to determine ...
1
vote
1answer
62 views
Rebuild and Reorganize index while altering index
Can someone please explain for example if i have a unique non-clustered index on a table with 3 columns.
due to some reason if i need to add one more column in the existing index .
Do i need to ...
0
votes
0answers
71 views
Explaining about SQL Server query Execution Plans and understanding Clustered and Nonclustered Indexes
I'm Christine and I'm a newbie. I would like to know if someone could help me clarify what I'm drilling down this execution plan as below :
Here's query generated from SQL server that is accompanied ...
5
votes
1answer
290 views
Is there any difference with specifying the primary key as an include column in a nonclustered index?
Don't nonclustered indexes inherently store a reference to the primary key on a table so that it can do a key lookup as needed?...if so, is it any less or more performant to specify the primary key as ...
0
votes
2answers
112 views
Are key lookups from non-clustered indexes always slower than a second query that does the lookup?
I've noticed in my system, whenever a non-clustered index is used in a query that has to also do a key lookup to get the additional fields being selected, it's faster for me to instead do two queries. ...