How to improve sql server query response time

Question

I have a table that contains 60 million records with the following structure
1. SEQ_ID (Bigint),
2. SRM_CLIENT_ENTITIES_SEQ_ID (Bigint),
3. CUS_ENTITY_DATA_SEQ_ID (Bigint),
4. SRM_CLIENT_ENTITY_ATTRIBUTES_SEQ_ID (Bigint),
5. ATTRIBUTE_DATETIME (DateTime),
6. ATTRIBUTE_DECIMAL (Decimal(18,2)),
7. ATTRIBUTE_STRING (nvarchar(255)),
8. ATTRIBUTE_BOOLEAN (Char(1)),
9. SRM_CLIENTS_SEQ_ID (Bigint)
Clustered index with key SEQ_ID
Non unique non clustered index : I've following four composite indexes
a. SRM_CLIENTS_SEQ_ID, SRM_CLIENT_ENTITIES_SEQ_ID, SRM_CLIENT_ENTITY_ATTRIBTUES_SEQ_ID, ATTRIBUTE_DATETIME
b. SRM_CLIENTS_SEQ_ID, SRM_CLIENT_ENTITIES_SEQ_ID, SRM_CLIENT_ENTITY_ATTRIBTUES_SEQ_ID, ATTRIBUTE_DECIMAL
c. SRM_CLIENTS_SEQ_ID, SRM_CLIENT_ENTITIES_SEQ_ID, SRM_CLIENT_ENTITY_ATTRIBTUES_SEQ_ID, ATTRIBUTE_STRING
d. SRM_CLIENTS_SEQ_ID, SRM_CLIENT_ENTITIES_SEQ_ID, SRM_CLIENT_ENTITY_ATTRIBTUES_SEQ_ID, ATTRIBUTE_BOOLEAN
The problem is that when i execute a simple query over this table it does not return the results in an acceptable time.
Query:
SELECT CUS_ENTITY_DATA_SEQ_ID FROM dbo.CUS_PIVOT_NON_UNIQUE_INDEXES WHERE SRM_CLIENT_ENTITY_ATTRIBUTES_SEQ_ID = 51986 AND ATTRIBUTE_DECIMAL = 4150196
Execution Time : 2 seconds
Thanks

Answer 1

Did you look at the execution plan.
The query may not use none of the indexes. The Clustered index is on SEQ_ID and the non clustered index doesn't start with SRM_CLIENT_ENTITY_ATTRIBUTES_SEQ_ID
OR ATTRIBUTE_DECIMAL.
The order of the columns in an index matters. Just for testing ( if it is not prod. environment) Create an NCI with SRM_CLIENT_ENTITY_ATTRIBUTES_SEQ_ID
and ATTRIBUTE_DECIMAL and check.
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