Relationship Representation (Tabular)

A relationship is a connection between two tables of data. The relationship establishes how the data in the two tables should be correlated.

See Relationship Representation (Tabular) for a detailed explanation on how to create and manipulate the relationship representation.

Relationship Representation

In tabular models, multiple relationships can be defined between two tables. When multiple relationships, between two tables, are defined only one can be defined as the default relationship for the model and it is named as the Active relationship; all other relationships are named as Inactive.

Relationship in AMO

In terms of AMO objects all inactive relationships have a representation of a one to one mapping relationship with Relationship and no other main AMO objects are required; for the active relationship other requirements exist and a mapping to the ReferenceMeasureGroupDimension is also required.

The following code snippets show how to create a relationship in Tabular models, how to activate a relationship and how to define a primary key in a table (other than "RowNumber"). To create an active relationship a primary key need to be defined in the primary key table - PKTableName - of the relationship (the one side of the relationship), the sample shown here creates the primary key on the PKColumnName if no primary key is defined in this column. Inactive relationships can be created without the need of having a primary key on the primary key column.


private Boolean createRelationship(string PKTableName, string PKColumnName, string MVTableName, string MVColumnName, AMO.Database tabularDb, string cubeName, Boolean forceActive)  
{  
    //verify input parameters  
    if(     string.IsNullOrEmpty(PKTableName) || string.IsNullOrWhiteSpace(PKTableName)  
        ||  string.IsNullOrEmpty(PKColumnName) || string.IsNullOrWhiteSpace(PKColumnName)  
        ||  string.IsNullOrEmpty(MVTableName) || string.IsNullOrWhiteSpace(MVTableName)  
        ||  string.IsNullOrEmpty(MVColumnName) || string.IsNullOrWhiteSpace(MVColumnName)  
        ||  (tabularDb == null)  
        ) return false;  
    if(!tabularDb.Dimensions.ContainsName(PKTableName) || !tabularDb.Dimensions.ContainsName(MVTableName)) return false;  
    if(!tabularDb.Dimensions[PKTableName].Attributes.ContainsName(PKColumnName) || !tabularDb.Dimensions[MVTableName].Attributes.ContainsName(MVColumnName)) return false;  

    //Verify underlying cube structure  
    if (!tabularDb.Cubes[cubeName].Dimensions.ContainsName(PKTableName) || !tabularDb.Cubes[cubeName].Dimensions.ContainsName(MVTableName)) return false; //Should return an exception!!  
    if (!tabularDb.Cubes[cubeName].MeasureGroups.ContainsName(PKTableName) || !tabularDb.Cubes[cubeName].MeasureGroups.ContainsName(MVTableName)) return false; //Should return an exception!!  

    //Make sure PKTableName.PKColumnName  is set as PK ==> <attribute>.usage == AMO.AttributeUsage.Key  
    if (tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].Usage != AMO.AttributeUsage.Key)  
    {  
        //... here we are 'fixing', if there is an issue with PKTableName.PKColumnName not beeing the PK of the table  
        setPKColumn(tabularDb, PKTableName, PKColumnName);  
    }  

    //Terminology note:   
    // -   the many side of the relationship is named the From end in AMO  
    // -   the PK side of the relationship in named the To end in AMO  
    //  
    //It seems relationships flow FROM the many side of the relationship in TO the primary key side of the relationship in AMO  
    //              
    //Verify the relationship we are creating does not exist, regardless of name.  
    //if it exists, return true (no need to recreate it)  
    //if it doesn't exists it will be created after this validation  

    //   
    foreach (AMO.Relationship currentRelationship in tabularDb.Dimensions[MVTableName].Relationships)  
    {  
        if ((currentRelationship.FromRelationshipEnd.Attributes[0].AttributeID == MVColumnName)  
            && (currentRelationship.ToRelationshipEnd.DimensionID == PKTableName)  
            && (currentRelationship.ToRelationshipEnd.Attributes[0].AttributeID == PKColumnName))  
        {  
            if (forceActive)  
            {  
                //Activate the relationship   
                setActiveRelationship(tabularDb.Cubes[cubeName], MVTableName, MVColumnName, PKTableName, currentRelationship.ID);  
                //Update server with changes made here  
                tabularDb.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.CreateOrReplace);  
                tabularDb.Cubes[cubeName].MeasureGroups[MVTableName].Process(AMO.ProcessType.ProcessFull);  
            }  
            return true;  
        }  
    }  

    //A relationship like the one to be created does not exist; ergo, let's create it:  

    //First, create the INACTIVE relationship definitions in the MultipleValues end of the relationship  
    #region define unique name for relationship  
    string newRelationshipID = string.Format("Relationship _{0}_{1}_ to _{2}_{3}_", MVTableName, MVColumnName, PKTableName, PKColumnName);  
    int rootLen = newRelationshipID.Length;  
    for (int i = 0; tabularDb.Dimensions[MVTableName].Relationships.Contains(newRelationshipID); )  
    {  
        newRelationshipID = string.Format("{0}_{1,8:0}", newRelationshipID.Substring(0, rootLen), i);  
    }  
    #endregion  
    AMO.Relationship newRelationship = tabularDb.Dimensions[MVTableName].Relationships.Add(newRelationshipID);  

    newRelationship.FromRelationshipEnd.DimensionID = MVTableName;  
    newRelationship.FromRelationshipEnd.Attributes.Add(MVColumnName);  
    newRelationship.FromRelationshipEnd.Multiplicity = AMO.Multiplicity.Many;  
    newRelationship.FromRelationshipEnd.Role = string.Empty;  
    newRelationship.ToRelationshipEnd.DimensionID = PKTableName;  
    newRelationship.ToRelationshipEnd.Attributes.Add(PKColumnName);  
    newRelationship.ToRelationshipEnd.Multiplicity = AMO.Multiplicity.One;  
    newRelationship.ToRelationshipEnd.Role = string.Empty;  

    //Update server to create relationship  
    tabularDb.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.UpdateOrCreate);  
    tabularDb.Dimensions[MVTableName].Process(AMO.ProcessType.ProcessDefault);  
    tabularDb.Dimensions[PKTableName].Process(AMO.ProcessType.ProcessDefault);  

    //Second, activate the relationship if relationship is to be set as the active relationship: 'forceActive==true'  
    //... an inactive relationship needs only to be created on the dimensions object  
    if (forceActive)  
    {  
        //Activate the relationship   
        setActiveRelationship(tabularDb.Cubes[cubeName], MVTableName, MVColumnName, PKTableName, newRelationshipID);                  
    }             
    return true;  
}  

private void setActiveRelationship(AMO.Cube currentCube, string MVTableName, string MVColumnName, string PKTableName, string relationshipID)  
{  
    if (!currentCube.MeasureGroups.Contains(MVTableName))  
    {  
        throw new AMO.AmoException(string.Format("Cube [{0}] does not contain Measure Group [{1}]\nError activating relationship [{2}]: [{4}] <--- [{1}].[{3}]"  
                                                , currentCube.Name, MVTableName, relationshipID, MVColumnName, PKTableName));  
    }  
    AMO.MeasureGroup currentMG = currentCube.MeasureGroups[MVTableName];  

    if (!currentMG.Dimensions.Contains(PKTableName))  
    {  
        AMO.ReferenceMeasureGroupDimension newReferenceMGDim = new AMO.ReferenceMeasureGroupDimension();  
        newReferenceMGDim.CubeDimensionID = PKTableName;  
        newReferenceMGDim.IntermediateCubeDimensionID = MVTableName;  
        newReferenceMGDim.IntermediateGranularityAttributeID = MVColumnName;  
        newReferenceMGDim.Materialization = AMO.ReferenceDimensionMaterialization.Regular;  
        newReferenceMGDim.RelationshipID = relationshipID;  
        foreach (AMO.CubeAttribute PKAttribute in currentCube.Dimensions[PKTableName].Attributes)  
        {  
            AMO.MeasureGroupAttribute PKMGAttribute = newReferenceMGDim.Attributes.Add(PKAttribute.AttributeID);  
            OleDbType PKMGAttributeType = PKAttribute.Attribute.KeyColumns[0].DataType;  
            PKMGAttribute.KeyColumns.Add(new AMO.DataItem(PKTableName, PKAttribute.AttributeID, PKMGAttributeType));  
            PKMGAttribute.KeyColumns[0].Source = new AMO.ColumnBinding(PKTableName, PKAttribute.AttributeID);  
        }  
        currentMG.Dimensions.Add(newReferenceMGDim);  

        AMO.ValidationErrorCollection errors = new AMO.ValidationErrorCollection();  

        newReferenceMGDim.Validate(errors, true);  
        if (errors.Count > 0)  
        {  
            StringBuilder errorMessages = new StringBuilder();  
            foreach (AMO.ValidationError err in errors)  
            {  
                errorMessages.AppendLine(string.Format("At {2}: # {0} : {1}", err.ErrorCode, err.FullErrorText, err.Source));  
            }  
            throw new AMO.AmoException(errorMessages.ToString());  
        }  
        //Update changes in the server  
        currentMG.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.CreateOrReplace);  
    }  
    else  
    {  
        AMO.ReferenceMeasureGroupDimension currentReferenceMGDim = (AMO.ReferenceMeasureGroupDimension)currentMG.Dimensions[PKTableName];  
        currentReferenceMGDim.RelationshipID = relationshipID;  
        currentReferenceMGDim.IntermediateGranularityAttributeID = MVColumnName;  
        //Update changes in the server  
        currentMG.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.UpdateOrCreate);  
    }  
    //process MG to activate relationship  
    currentMG.Process(AMO.ProcessType.ProcessFull);  

}  

private void setPKColumn(AMO.Database tabularDb, string PKTableName, string PKColumnName)  
{  
        //Find all 'unwanted' Key attributes, remove their Key definitions and include the attributes in the ["RowNumber"].AttributeRelationships  
        foreach (AMO.DimensionAttribute currentDimAttribute in tabularDb.Dimensions[PKTableName].Attributes)  
        {  
            if ((currentDimAttribute.Usage == AMO.AttributeUsage.Key) && (currentDimAttribute.ID != PKColumnName))  
            {  
                currentDimAttribute.Usage = AMO.AttributeUsage.Regular;  
                if (currentDimAttribute.ID != "RowNumber")  
                {  
                    currentDimAttribute.KeyColumns[0].NullProcessing = AMO.NullProcessing.Preserve;  
                    currentDimAttribute.AttributeRelationships.Clear();  
                    if (!tabularDb.Dimensions[PKTableName].Attributes["RowNumber"].AttributeRelationships.ContainsName(currentDimAttribute.ID))  
                    {  
                        AMO.DimensionAttribute currentAttribute = tabularDb.Dimensions[PKTableName].Attributes[currentDimAttribute.ID];  
                        AMO.AttributeRelationship currentAttributeRelationship = tabularDb.Dimensions[PKTableName].Attributes["RowNumber"].AttributeRelationships.Add(currentAttribute.ID);  
                        currentAttributeRelationship.OverrideBehavior = AMO.OverrideBehavior.None;  
                    }  
                    tabularDb.Dimensions[PKTableName].Attributes["RowNumber"].AttributeRelationships[currentDimAttribute.ID].Cardinality = AMO.Cardinality.Many;  
                }  
            }  
        }  

        //Remove PKColumnName from ["RowNumber"].AttributeRelationships  
        int PKAtribRelationshipPosition = tabularDb.Dimensions[PKTableName].Attributes["RowNumber"].AttributeRelationships.IndexOf(PKColumnName);  
        if (PKAtribRelationshipPosition != -1) tabularDb.Dimensions[PKTableName].Attributes["RowNumber"].AttributeRelationships.RemoveAt(PKAtribRelationshipPosition, true);  

        //Define PKColumnName as Key and add ["RowNumber"] to PKColumnName.AttributeRelationships with cardinality of One  
        tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].Usage = AMO.AttributeUsage.Key;  
        tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].KeyColumns[0].NullProcessing = AMO.NullProcessing.Error;  
        if (!tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].AttributeRelationships.ContainsName("RowNumber"))  
        {  
            AMO.DimensionAttribute currentAttribute = tabularDb.Dimensions[PKTableName].Attributes["RowNumber"];  
            AMO.AttributeRelationship currentAttributeRelationship = tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].AttributeRelationships.Add(currentAttribute.ID);  
            currentAttributeRelationship.OverrideBehavior = AMO.OverrideBehavior.None;  
        }  
        tabularDb.Dimensions[PKTableName].Attributes[PKColumnName].AttributeRelationships["RowNumber"].Cardinality = AMO.Cardinality.One;  

        //Update Table before going creating the relationship  
        tabularDb.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.UpdateOrCreate);  
        tabularDb.Dimensions[PKTableName].Process(AMO.ProcessType.ProcessDefault);                

}  

AMO2Tabular sample

However, to have an understanding on how to use AMO to create and manipulate relationship representations see the source code of the AMO to Tabular sample. The sample is available at Codeplex. An important note about the code: the code is provided only as a support to the logical concepts explained here and should not be used in a production environment; nor should it be used for other purpose other than the pedagogical one.