Operators (MDX Syntax)
In Multidimensional Expressions (MDX), operators let you perform the following actions:
- Change data, either permanently or temporarily.
- Search for values or objects that meet a specified condition.
- Implement a decision between values or expressions.
- Test for specific conditions before beginning or committing a transaction, or before executing specific statements.
MDX supports the operators listed in the following table:
| To perform this type of operation | Use |
|---|---|
Assigns a value to a variable, or associates a result set column with an alias. |
|
Addition, subtraction, multiplication, division. |
|
Test for the truth of a condition, such as AND, OR, NOT, and XOR. |
|
Compare a value against another value or an expression. |
|
Either permanently or temporarily combine two strings into one string. |
|
Either permanently or temporarily combine two set expressions into a single set. |
|
Performs an operation on one operand. |
Note
In queries, anyone who can see the data in the cube to be used with some type of operator can perform operations. However, you need the appropriate permissions before you can successfully change the data.
When using multiple operators, the order in which MDX evaluates the operators is important. Similarly, the user of operators may require that one data type be converted into another data type before the operators can be evaluated.
Evaluating Complex Expressions
You can build an expression by using operators to combine several smaller expressions. In these complex expressions, MDX evaluates the operators in order based on the definition of operator precedence used by Microsoft SQL Server 2005 Analysis Services (SSAS). MDX performs operators with higher precedence before performing operators with lower precedence.
Understanding Operator Precedence
The following list shows operator precedence, from highest to lowest. Operators in the same line are equal in precedence, and are evaluated from left to right unless otherwise forced by parenthesis:
- IS
- AS
- DISTINCT
- :
- ^
- /, *
- +, -
- EXISTING
- <>, >=, =, <=, >, <
- NOT
- AND
- XOR
- OR
For more information about operators in MDX, see MDX Operator Reference (MDX).
Determining Results
When you combine simple expressions to form a complex expression, the rules for the operators combined with the rules for data type precedence determine the data type of the resulting value.
If the result is a character or Unicode value, the rules for the operators combined with the rules for collation precedence determines the collation of the result. For more information about collations, see Working with Languages and Collations (SSAS).
There are also rules that determine the precision, scale, and length of the result based on the precision, scale, and length of the simple expressions.
Converting Data Types
MDX implicitly converts an object to a different type when that object is used in an expression that requires a different type. The following table defines the conversion rules for each object.
| Original Type | Type Needed | Conversion |
|---|---|---|
Level |
Set |
<level>.members |
Hierarchy |
Member |
<hierarchy>.defaultmember |
Member |
Tuple |
(<Member>) |
Tuple |
Member |
<tuple>.item(0) |
Tuple |
Scalar |
<tuple>.value |