jeudi 17 février 2011

How to use Joins in DAX

Use joins to link tables so that they can return values together. By default, inner joins are created. The following table describes the types of joins available:

Join Type Use to...
inner Combine records into one table only when there are matching values in a common field.
outer Combine records into one table even if there are no matching values in the common field.
exists Combine records from one table whenever a value exists in a common field in another table.
notexists Combine records from one table whenever a value in a common field in another table does not exist.

Not only is there additional syntax needed to specify what table is being joined, but the where clause also has to be modified. Within the where clause, the two fields that relate the tables must be specified in addition to any other conditions of the search. When using an inner or outer join the table buffers of both tables are populated with the retrieved records. An exists or not exists join only populates the first table.

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