--- title: Hierarchical Link description: A Hierarchical Link stores parent-child pairs of one Hub, such as an employee and their manager, with the hash key Link_HK, in a Raw Vault table. --- [Skip to content](https://knowledge.bigenius-x.com/hierarchical-link#main-content) [Contact us](https://knowledge.bigenius-x.com/kb-tickets/new?hsLang=en) [Go to Customer Portal](https://knowledge.bigenius-x.com/customer-portal?hsLang=en) [![TRI\_Logo\_biGENIUS\_2020\_RGB\_s](https://knowledge.bigenius-x.com/hs-fs/hubfs/Marketing/TRI_Logo_biGENIUS_2020_RGB_s.png?width=150&height=42&name=TRI_Logo_biGENIUS_2020_RGB_s.png)](https://www.bigenius-x.com/) Open main navigation Close main navigation - [Contact us](https://knowledge.bigenius-x.com/kb-tickets/new) - [Go to Customer Portal](https://knowledge.bigenius-x.com/customer-portal) How can we help you? - There are no suggestions because the search field is empty. 1. [biGENIUS-X Knowledge Base](https://knowledge.bigenius-x.com/?hsLang=en) 2. [Generators](https://knowledge.bigenius-x.com/generators?hsLang=en) 3. [Model Object Type](https://knowledge.bigenius-x.com/generators?hsLang=en#model-object-type) # Hierarchical Link **Applies to** Platform: Microsoft SQL Server · Snowflake · Snowflake dbt · Databricks · Databricks dbt · Fabric Lakehouse · Fabric Warehouse · Oracle Architecture: Data Vault A Hierarchical Link stores parent-child pairs of one Hub, such as an employee and their manager or an item and its component, with the hash key `Link_HK`, in a table of the Raw Vault layer. Use it for a hierarchy inside one business object. After each load, the result view shows one row per pair and the load that first delivered it. ### Sources and relationships A Hierarchical Link reads [Stages](https://knowledge.bigenius-x.com/stage?hsLang=en), [RawVault Composites](https://knowledge.bigenius-x.com/rawvault-composite?hsLang=en) and [Store Entities](https://knowledge.bigenius-x.com/store-entity?hsLang=en) of a linked Data Store project, in one or more dataflows. It has exactly two relationships, both to the same [Hub](https://knowledge.bigenius-x.com/hub?hsLang=en), with roles, for example `EMPLOYEE` and `MANAGER`. The foreign-key terms are the business keys of the Hierarchical Link. See [Use parent-child relationships](https://knowledge.bigenius-x.com/use-parent-child-relationships?hsLang=en). Link Satellites, Record Tracking Link Satellites, Effectivity Link Satellites reference a Hierarchical Link. PIT, Current View, History View, BusinessVault Composite, [Vault Out](https://knowledge.bigenius-x.com/vault-out?hsLang=en) and the Business Vault types can read it as a source. A Current View on a Hierarchical Link and its Link Satellite is the usual source of a [Hierarchy Flatten](https://knowledge.bigenius-x.com/hierarchy-flatten?hsLang=en). ### Create a Hierarchical Link - With the wizard: open the menu of a Stage, RawVault Composite or Store Entity, choose **Automate** and then **Create Hierarchical Link**. Its steps are [Create Model Object](https://knowledge.bigenius-x.com/wizard-step-create-model-object?hsLang=en), [Create Dataflow](https://knowledge.bigenius-x.com/wizard-step-create-dataflow?hsLang=en), [Create Multiple Relations](https://knowledge.bigenius-x.com/wizard-step-create-multiple-relations?hsLang=en), [Define Roles](https://knowledge.bigenius-x.com/wizard-step-create-relations-with-role?hsLang=en), [Map Foreign Key Terms](https://knowledge.bigenius-x.com/wizard-step-map-foreign-key-terms?hsLang=en) and [Add to View](https://knowledge.bigenius-x.com/wizard-step-add-to-view?hsLang=en). See [Create a Model Object with the wizard](https://knowledge.bigenius-x.com/create-a-model-object-with-the-wizard?hsLang=en). - Manually: [create a model object](https://knowledge.bigenius-x.com/create-a-model-object?hsLang=en) of type Hierarchical Link in the Raw Vault layer, [add two relationships](https://knowledge.bigenius-x.com/add-a-relationship?hsLang=en) to the Hub with a role each, [create a dataflow set](https://knowledge.bigenius-x.com/create-a-data-flow-set?hsLang=en), [add the source model object](https://knowledge.bigenius-x.com/add-a-model-object-into-a-data-flow-set?hsLang=en) and [map the foreign-key terms](https://knowledge.bigenius-x.com/map-a-source-term-with-a-target-term?hsLang=en). ### Properties - [Implementation Type](https://knowledge.bigenius-x.com/implementation-type-model-object?hsLang=en): `Permanent` only. - [Foreign Key Mode](https://knowledge.bigenius-x.com/foreign-key-mode-model-object?hsLang=en): whether the table gets foreign keys to the Hub table. With `Create Disabled`, the default, they are created and disabled. - [Load Caching](https://knowledge.bigenius-x.com/load-caching-model-object?hsLang=en): empty (default) or `Hashing`, which stores the hashing view in a table before the loader runs. - [Custom Singleton Values](https://knowledge.bigenius-x.com/custom-singleton-values-model-object?hsLang=en): values of the unknown-member row. - [Deduplication Method](https://knowledge.bigenius-x.com/deduplication-method-dataflow?hsLang=en) and [Sort Order within Partition](https://knowledge.bigenius-x.com/sort-order-within-partition-dataflow?hsLang=en), per dataflow. - [Use Embryo Loader](https://knowledge.bigenius-x.com/embryo-loader?hsLang=en), per relationship: inserts business keys that the Hub does not hold yet. ### Default Terms - [`Link_HK`](https://knowledge.bigenius-x.com/link_hk?hsLang=en): hash of the business keys of both relationships and primary key of the table. - [`DVLINK_ForeignKey_Identity`](https://knowledge.bigenius-x.com/dvlink_foreignkey_identity?hsLang=en): names one hash-key column per relationship, `__HK`, for example `common_employee_MANAGER_HK`, with the key of the related Hub row. - [`BG_LoadTimestamp`](https://knowledge.bigenius-x.com/bg_loadtimestamp?hsLang=en) and [`BG_SourceSystem`](https://knowledge.bigenius-x.com/bg_sourcesystem?hsLang=en): the load that inserted the row and its source system, empty unless you map it. - [`BG_DataQuality_ID`](https://knowledge.bigenius-x.com/bg-dataquality-id?hsLang=en), [`BG_ErrorCount`](https://knowledge.bigenius-x.com/bg_errorcount?hsLang=en) and [`BG_ErrorDescription`](https://knowledge.bigenius-x.com/bg_errordescription?hsLang=en): hidden terms of the data quality objects. A row without a parent has a NULL parent key when that foreign-key term is nullable. The Hierarchical Link then stores the key of the Hub's unknown-member row for the parent. See [Behaviour for Nulled Business Keys in Links](https://knowledge.bigenius-x.com/behaviour-for-nulled-business-keys-in-links-project?hsLang=en) and [How biGENIUS-X builds hash values](https://knowledge.bigenius-x.com/how-bigenius-x-builds-hash-values?hsLang=en). ### Generated objects These are the names on Microsoft SQL Server for the Hierarchical Link `load_employee_hlnk` with one dataflow: | Role | Generated name | Purpose | | --- | --- | --- | | Source | `RDV_HLNK_load_employee_hlnk_Source` | Reads the sources | | Deduplication | `RDV_HLNK_load_employee_hlnk_Deduplication` | Removes duplicate rows | | Hashing | `RDV_HLNK_load_employee_hlnk_Hashing` | Calculates the hash keys | | HashingStorage | `RDV_HLNK_load_employee_hlnk_HashingTable` | Stores the hashed rows | | HashingLoader | `RDV_HLNK_load_employee_hlnk_HashingLoader` | Fills the hashing table | | EmbryoLoader | `RDV_HLNK_load_employee_hlnk_EmbryoLoader` | Adds missing Hub keys | | Delta | `RDV_HLNK_load_employee_hlnk_Delta` | Selects new pairs | | Loader | `RDV_HLNK_load_employee_hlnk_Loader` | Inserts the new rows | | Storage | `RDV_HLNK_load_employee_hlnk` | Hierarchical Link table | | Result | `RDV_HLNK_load_employee_hlnk_Result` | Query view | - Loaders are stored procedures; the Hierarchical Link table and the hashing table are tables; all other objects are views. - The deduplication view exists only with a Deduplication Method other than `None`. - The hashing table and hashing loader exist only with Load Caching `Hashing`. The delta view then reads the hashing table. - The embryo loader exists only when Use Embryo Loader is true on a relationship. It runs before the loader. - With several dataflows, all objects except the table and the result view exist once per dataflow, with the dataflow name in their names. - The table script inserts the unknown-member row with hash keys of zeros. The result view hides it. - The result view always exists, independent of [Create Result Views](https://knowledge.bigenius-x.com/create-result-views-project?hsLang=en). With the default settings, a load runs this chain: ``` sources -> _Source -> _Hashing -> _Delta -> _Loader _Loader -> RDV_HLNK_load_employee_hlnk -> _Result _Result -> _Delta (pairs already stored) ``` The hashing view calculates `Link_HK` and the Hub key of each role. The delta view keeps the rows whose `Link_HK` is not in the result view, and the loader inserts them. The loader never updates or deletes rows, so a pair that the source no longer delivers stays in the table. A Link Satellite on the Hierarchical Link stores the history of each pair. With the optional objects, `_Deduplication` sits between `_Source` and `_Hashing`, `_HashingLoader` fills `_HashingTable` before the delta view reads it, and `_EmbryoLoader` writes missing keys to the Hub table. ### Example The Hierarchical Link `load_employee_hlnk` on Microsoft SQL Server reads the Stage `EMPLOYEE`. Both relationships go to the Hub `common_employee`, with the roles `EMPLOYEE` and `MANAGER`. `MANAGER_ID` is nullable in the source. The loads deliver these rows: - Load 1 on 2026-10-28 08:00: employee 101 without a manager, employees 102 and 103 with manager 101. - Load 2 on 2026-10-29 08:00: employee 103 now reports to 102, and employee 104 is new with manager 102. ### Check the result Query the result view, here in the schema `rv`: ``` SELECT FK_common_employee_EMPLOYEE_EMPLOYEE_ID AS EMPLOYEE_ID, FK_common_employee_MANAGER_EMPLOYEE_ID AS MANAGER_ID, common_employee_MANAGER_HK AS MANAGER_HK, BG_LoadTimestamp FROM rv.RDV_HLNK_load_employee_hlnk_Result ORDER BY EMPLOYEE_ID, BG_LoadTimestamp; ``` This is the result after load 2, with hash keys shortened to their first four bytes: ``` EMPLOYEE_ID MANAGER_ID MANAGER_HK BG_LoadTimestamp 101 NULL 0x00000000 2026-10-28 08:00 102 101 0x6348AE9A 2026-10-28 08:00 103 101 0x6348AE9A 2026-10-28 08:00 103 102 0x8887BDD9 2026-10-29 08:00 104 102 0x8887BDD9 2026-10-29 08:00 ``` - Employee 101 has no manager, so `MANAGER_HK` holds the key of the unknown-member row, all zeros. - Employee 103 has two rows: the pair with manager 101 stays after load 2 adds the pair with manager 102. - `MANAGER_HK` 0x6348AE9A is the Hub key of employee 101. ### Platform differences - Snowflake: names are in capitals, and the loader is a stored procedure. The load control task `LC_RDV_HLNK__TASK` calls it. The dataflow properties [Use Stream](https://knowledge.bigenius-x.com/use-stream-model-object?hsLang=en) and [Warehouse Placeholder Variable Name](https://knowledge.bigenius-x.com/warehouse-placeholder-variable-name-dataflow?hsLang=en) apply. - Databricks and Fabric Lakehouse: table and view names are in lowercase, and the loader is the notebook `RDV_HLNK__Loader`. The properties [File Format](https://knowledge.bigenius-x.com/file-format-model-object?hsLang=en), [Optimization Method](https://knowledge.bigenius-x.com/optimization-method-model-object?hsLang=en), [Optimization Method Columns](https://knowledge.bigenius-x.com/optimization-method-columns-model-object?hsLang=en) and [Use Sequential Dataflow Execution](https://knowledge.bigenius-x.com/use-sequential-dataflow-execution-model-object?hsLang=en) apply. Fabric Lakehouse allows only Foreign Key Mode `None`. - Databricks dbt and Snowflake dbt: the Hierarchical Link becomes the dbt models `rdv_hlnk__source` and `rdv_hlnk_`. The model `rdv_hlnk__result` exists only when Create Result Views is true; the default on dbt is false. Load Caching and Use Embryo Loader are not available. - Fabric Warehouse: the same objects as on Microsoft SQL Server, deployed by notebooks. - Oracle: names are in capitals, and the loader is a PL/SQL package. [Partition Clause](https://knowledge.bigenius-x.com/partition-clause-and-table-storage-model-object?hsLang=en) adds its text to the `CREATE TABLE` statement. Table Compression, the tablespaces and the statistics properties also apply. - Foreign Key Mode `Create Enforced` exists only on Microsoft SQL Server and Oracle. ### Limitations - A Hierarchical Link has exactly two relationships to the same Hub and no terms other than foreign keys and Default Terms. Validation reports an error otherwise. - A Hierarchical Link holds one level, the direct parent. A [Hierarchy Flatten](https://knowledge.bigenius-x.com/hierarchy-flatten?hsLang=en) resolves all levels. - A dataflow that delivers the same pair twice in one load makes the loader fail with a primary key violation. A Deduplication Method removes such duplicates before hashing. ### Release differences - Generator 2.2: Use Embryo Loader is available. - Generator 2.3: Custom Singleton Values is available. ### Related articles - Previous: [Hub](https://knowledge.bigenius-x.com/hub?hsLang=en) - Next: [Link Satellite](https://knowledge.bigenius-x.com/link-satellite?hsLang=en), [Hierarchy Flatten](https://knowledge.bigenius-x.com/hierarchy-flatten?hsLang=en) - Reference: [Link\_HK](https://knowledge.bigenius-x.com/link_hk?hsLang=en), [DVLINK\_ForeignKey\_Identity](https://knowledge.bigenius-x.com/dvlink_foreignkey_identity?hsLang=en), [Foreign Key Mode (Model Object)](https://knowledge.bigenius-x.com/foreign-key-mode-model-object?hsLang=en), [Load Caching (Model Object)](https://knowledge.bigenius-x.com/load-caching-model-object?hsLang=en), [Custom Singleton Values (Model Object)](https://knowledge.bigenius-x.com/custom-singleton-values-model-object?hsLang=en), [Behaviour for Nulled Business Keys in Links (Project)](https://knowledge.bigenius-x.com/behaviour-for-nulled-business-keys-in-links-project?hsLang=en), [Create Result Views (Project)](https://knowledge.bigenius-x.com/create-result-views-project?hsLang=en) - 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