compound-index

Say I've got a table: CREATE TABLE Users ( Id INT IDENTITY (1, 1), FirstName VARCHAR(40), LastName VARCHAR(40) ) Queries are usually on FirstName or LastName , but also on FirstName and LastName . If I create a non-clustered index on FirstName and another on LastName , then my first two queries are catered for. Apparently, SQL Server will use index intersection for the other query. Alternatively, if I have indexees on (FirstName) and on (LastName, FirstName), can/does SQL Server use the second index for queries on just LastName as well as queries on both? Does SQL Server store compound index

After reading here for ages, I've finally registered to ask a question. I've been messing around with IndexedDB lately and stumbled over a problem with compound indexes (I use them somilar to the example here ). I have an object in the objectstore with a string value, and a couple of integer values. E. g.: [description:text, value1:int, value2:int, value3:int] I created a compound index on this object like this: ("compoundIndex", ["value1" , "value2" , "value3"] , { unique: false }); In the html I got a couple of select boxes and a textfield, that allows the user to search for specific entries

Lets say I have document with the following two keys: 1) key1 2) key2 If I am creating compound index on both of them.. {'key1':1,'key2':1} When running a query relevant only for key1.. does the index above is used? or I need to create specific index only for key1 also? Thanks Yes. In a B-tree index, you can use a prefix of the columns. So you can use the index for a query on 'key1' (but not as efficiently for 'key2', the column order in the index matters). This is the same situation as in a printed telephone book, which is an index on [lastName, firstName]. You can use that to look up people

We need to create a compound index in the same order as the parameters are being queried. Does this order matter performance-wise at all? Imagine we have a collection of all humans on earth with an index on sex (99.9% of the time "male" or "female", but string nontheless (not binary)) and an index on name . If we would want to be able to select all people of a certain sex with a certain name , e.g. all "male"s named "John" , is it better to have a compound index with sex first or name first? Why (not)? Abdullah Rasheed Redsandro, You must consider Index Cardinality and Selectivity . 1. Index