Question

I have a table as below

dbo.UserLogs

-------------------------------------
Id | UserId |Date | Name| P1 | Dirty
-------------------------------------

There can be several records per userId[even in millions]

I have clustered index on Date column and query this table very frequently in time ranges.
The column ‘Dirty’ is non-nullable and can take either 0 or 1 only so I have no indexes on ‘Dirty’

I have several millions of records in this table and in one particular case in my application i need to query this table to get all UserId that have at least one record that is marked dirty.

I tried this query – select distinct(UserId) from UserLogs where Dirty=1

I have 10 million records in total and this takes like 10min to run and i want this to run much faster than this.

[i am able to query this table on date column in less than a minute.]

Any comments/suggestion are welcome.

my env
64bit,sybase15.0.3,Linux

Answer 1

Add an index containing both the UserId and Dirty fields. Put UserId before Dirty in the index as it has more unique values.