关系是两个数据表之间的联系。 该关系确立两个表中的数据应该如何相关。
有关如何创建和操作关系表示形式的详细说明，请参阅关系表示形式（表格）。
关系表示形式
在表格模型中，两个表之间可以定义多重关系。 如果在两个表之间定义了多重关系，只能将其中一个定义为模型的默认关系，默认关系命名为“活动”关系；其他所有关系都命名为“非活动”关系。
AMO 中的关系
就 AMO 对象而言，所有非活动关系的表示形式都与 Relationship 存在一对一映射关系，并且不需要任何其他主要 AMO 对象；对于活动关系，还存在其他要求，并且还需要与 ReferenceMeasureGroupDimension 之间的映射。
下面的代码段演示如何在表格模型中创建关系、如何激活关系，以及如何定义表中的主键（而不是“RowNumber”）。 若要创建处于活动状态的关系，需要在关系的主键表 PKTableName 中定义主键（关系中的一方）。在此显示的示例对 PKColumnName 创建了主键（如果此列中未定义主键）。 创建非活动关系时不需要主键列中的主键。
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 示例
但是，为了理解如何使用 AMO 创建和操作关系表示形式，请参阅 AMO 到表格示例中的源代码。 该示例在 Codeplex 上提供。 有关该代码的重要说明：提供该代码只是为了支持本文介绍的逻辑概念，不应用于生产环境中；也不应用于除教学之外的其他用途。