Importing Associations And Joins From A Database Schema in Denodo

A coworker recently asked a question as to whether denodo generated joins automatically from source RDBMS database schema.  After searching, a few snippets of information became obvious.  First, that the subject of inheriting join properties was broader than joins and needed to in modeling associations (joins on demand). Second, that there were some denodo design best practices to be considered to optimize associations.

Does Denodo Automatically Generate Joins From the Source System?

After some research, the short answer is no.

Can Denodo Inherit Accusations From A Logical Model?

The short answer is yes. 

Denodo bridges allow models to be passed to and from other modeling tools, it is possible to have the association build automatically, using the top-down approach design approach and importing a model, at the Interface View level, which is the topmost level of the top-down design process. 

However, below the Interface view level, associations and or joins are created manually by the developer.

Where Should Associations Be Created?

You don’t necessarily need to define an Association at every level, usually, the best practice is to apply associations at following points:

These best practices should cover the majority scenarios, beyond these guidelines it is best to take an ad-hoc approach to create Associations when you see a specific performance/optimization.

Related References

Associations in Denodo

Why Business Intelligence (BI) needs a Semantic Data Model

A semantic data model is a method of organizing and representing corporate data that reflects the meaning and relationships among data items. This method of organizing data helps end users access data autonomously using familiar business terms such as revenue, product, or customer via the BI (business intelligence) and other analytics tools. The use of a semantic model offers a consolidated, unified view of data across the business allowing end-users to obtain valuable insights quickly from large, complex, and diverse data sets.

What is the purpose of semantic data modeling in BI and data virtualization?

A semantic data model sits between a reporting tool and the original database in order to assist end-users with reporting. It is the main entry point for accessing data for most organizations when they are running ad hoc queries or creating reports and dashboards. It facilitates reporting and improvements in various areas, such as:

  • No relationships or joins for end-users to worry about because they’ve already been handled in the semantic data model
  • Data such as invoice data, salesforce data, and inventory data have all been pre-integrated for end-users to consume.
  • Columns have been renamed into user-friendly names such as Invoice Amount as opposed to INVAMT.
  • The model includes powerful time-oriented calculations such as Percentage in sales since last quarter, sales year-to-date, and sales increase year over year.
  • Business logic and calculations are centralized in the semantic data model in order to reduce the risk of incorrect recalculations.
  • Data security can be incorporated. This might include exposing certain measurements to only authorized end-users and/or standard row-level security.

A well-designed semantic data model with agile tooling allows end-users to learn and understand how altering their queries results in different outcomes. It also gives them independence from IT while having confidence that their results are correct.

denodo SQL Type Mapping

denodo 7.0 saves some manual coding when building the ‘Base Views’ by performing some initial data type conversions from ANSI SQL type to denodo Virtual DataPort data types. So, where is a quick reference mapping to show to what the denodo Virtual DataPort Data Type mappings are:

ANSI SQL types To Virtual DataPort Data types Mapping

ANSI SQL TypeVirtual DataPort Type
BIT (n)blob
BIT VARYING (n)blob
BOOLboolean
BYTEAblob
CHAR (n)text
CHARACTER (n)text
CHARACTER VARYING (n)text
DATElocaldate
DECIMALdouble
DECIMAL (n)double
DECIMAL (n, m)double
DOUBLE PRECISIONdouble
FLOATfloat
FLOAT4float
FLOAT8double
INT2int
INT4int
INT8long
INTEGERint
NCHAR (n)text
NUMERICdouble
NUMERIC (n)double
NUMERIC (n, m)double
NVARCHAR (n)text
REALfloat
SMALLINTint
TEXTtext
TIMESTAMPtimestamp
TIMESTAMP WITH TIME ZONEtimestamptz
TIMESTAMPTZtimestamptz
TIMEtime
TIMETZtime
VARBITblob
VARCHARtext
VARCHAR ( MAX )text
VARCHAR (n)text

ANSI SQL Type Conversion Notes

  • The function CAST truncates the output when converting a value to a text, when these two conditions are met:
  1. You specify a SQL type with a length for the target data type. E.g. VARCHAR(20).
  2. And, this length is lower than the length of the input value.
  • When casting a boolean to an integertrue is mapped to 1 and false to 0.

Related References

denodo 7.0 Type Conversion Functions

Data Modeling – Column Data Classification

Data Modeling, Column Data Classification, Field Data Classification
Data Modeling

Column Data Classification

When analyzing individual column data, at its most foundational level, column data can be classified by their fundamental use/characteristics.  Granted, when you start rolling up the structure into multiple columns, table structure and table relationship, then other classifications/behaviors, such as keys (primary and foreign), indexes, and distribution come into play.  However, many times when working with existing data sets it is essential to understand the nature the existing data to begin the modeling and information governance process.

Column Data Classification

Generally, individual columns can be classified into the classifications:

  • Identifier — A column/field which is unique to a row and/or can identify related data (e.g., Person ID, National identifier, ). Basically, think primary key and/or foreign key.
  • Indicator — A column/field, often called a Flag, that has a binary condition (e.g., True or False, Yes or No, Female or Male, Active or Inactive). Frequently used to identify compliance with complex with a specific business rule.
  • Code — A column/field that has a distinct and defined set of values, often abbreviated (e.g., State Code, Currency Code)
  • Temporal — A column/field that contains some type date, timestamp, time, interval, or numeric duration data
  • Quantity — A column/field that contains a numeric value (decimals, integers, etc.) and is not classified as an Identifier or Code (e.g., Price, Amount, Asset Value, Count)
  • Text — A column/field that contains alphanumeric values, possibly long text, and is not classified as an Identifier or Code (e.g., Name, Address, Long Description, Short Description)
  • Large Object (LOB)– A column/field that contains data traditional long text fields or binary data like graphics. The large objects can be broadly classified as Character Large Objects (CLOBs), Binary Large Objects (BLOBs), and Double-Byte Character Large Object (DBCLOB or NCLOB).

Related References

What is a Common Data Model (CDM)?

Data Model, Common Data Model, CDM, What is a Common Data Model (CDM)
Data Model

What is a Common Data Model (CDM)?

A Common Data Model (CDM) is a share data structure designed to provide well-formed and standardized data structures within an industry (e.g. medical, Insurance, etc.) or business channel (e.g. Human resource management, Asset Management, etc.), which can be applied to provide organizations a consistent unified view of business information.   These common models can be leveraged as accelerators by organizations form the foundation for their information, including SOA interchanges, Mashup, data vitalization, Enterprise Data Model (EDM), business intelligence (BI), and/or to standardize their data models to improve meta data management and data integration practices.

Related references

IBM, IBM Analytics

IBM Analytics, Technology, Database Management, Data Warehousing, Industry Models

github.com

Observational Health Data Sciences and Informatics (OHDSI)/Common Data Model

Oracle

Oracle Technology Network, Database, More Key Features, Utilities Data Model

Oracle

Industries, Communications, Service Providers, Products, Data Mode, Oracle Communications Data Model

Oracle

Oracle Technology Network, Database, More Key Features, Airline data Model

Netezza / PureData – How to add a Foreign Key

DDL (Data Definition Language), Netezza PureData How to add a Foreign Key
DDL (Data Definition Language)

Adding a forging key to tables in Netezza / PureData is a best practice; especially, when working with dimensionally modeled data warehouse structures and with modern governance, integration (including virtualization), presentation semantics (including reporting, business intelligence and analytics).

Foreign Key (FK) Guidelines

  • A primary key must be defined on the table and fields (or fields) to which you intend to link the foreign key
  • Avoid using distribution keys as foreign keys
  • Foreign Key field should not be nullable
  • Your foreign key link field(s) must be of the same format(s) (e.g. integer to integer, etc.)
  • Apply standard naming conventions to constraint name:
    • FK_<<Constraint_Name>>_<<Number>>
    • <<Constraint_Name>>_FK<<Number>>
  • Please note that foreign key constraints are not enforced in Netezza

Steps to add a Foreign Key

The process for adding foreign keys involves just a few steps:

  • Verify guidelines above
  • Alter table add constraint SQL command
  • Run statistics, which is optional, but strongly recommended

Basic Foreign Key SQL Command Structure

Here is the basic syntax for adding Foreign key:

ALTER TABLE <<Owner>>.<<NAME_OF_TABLE_BEING_ALTERED>>

ADD CONSTRAINT <<Constraint_Name>>_fk<Number>>

FOREIGN KEY (<<Field_Name or Field_Name List>>) REFERENCES <<Owner>>.<<target_FK_Table_Name>.(<<Field_Name or Field_Name List>>) <<On Update | On Delete>> action;

Example Foreign Key SQL Command

This is a simple one field example of the foreign key (FK)

ALTER TABLE Blog.job_stage_fact

ADD CONSTRAINT job_stage_fact_host_dim_fk1

FOREIGN KEY (hostid) REFERENCES Blog.host_dim(hostid) ON DELETE cascade ON UPDATE no action;

Related References

Alter Table

PureData System for Analytics, PureData System for Analytics 7.2.1, IBM Netezza database user documentation, Netezza SQL command reference, Alter Table, constraints

Database – What is a foreign key?

Acronyms, Abbreviations, Terms, And Definitions, DDL (Data Definition Language), What is a foreign key
Acronyms, Abbreviations, Terms, And Definitions

Definition of a Foreign Key

  • A foreign Key (FK) is a constraint that references the unique primary key (PK) of another table.

Facts About Foreign Keys

  • Foreign Keys act as a cross-reference between tables linking the foreign key (Child record) to the Primary key (parent record) of another table, which establishing a link/relationship between the table keys
  • Foreign keys are not enforced by all RDBMS
  • The concept of referential integrity is derived from foreign key theory
  • Because Foreign keys involve more than one table relationship, their implementation can be more complex than primary keys
  • A foreign-key constraint implicitly defines an index on the foreign-key column(s) in the child table, however, manually defining a matching index may improve join performance in some database
  • The SQL, normally, provides the following referential integrity actions for deletions, when enforcing foreign-keys

Cascade

  • The deletion of a parent (primary key) record may cause the deletion of corresponding foreign-key records.

No Action

  • Forbids the deletion of a parent (primary key) record, if there are dependent foreign-key records.   No Action does not mean to suppress the foreign-key constraint.

Set null

  • The deletion of a parent (primary key) record causes the corresponding foreign-key to be set to null.

Set default

  • The deletion of a record causes the corresponding foreign-keys be set to a default value instead of null upon deletion of a parent (primary key) record

Related References