OLTP vs Data Warehousing

OLTP Versus Data Warehousing I’ve tried to explain the difference between OLTP systems and a Data Warehouse to my managers many times, as I’ve worked at a hospital as a Data Warehouse Manager/data analyst for many years. Why was the list that came from the operational applications different than the one that came from the … Continue reading OLTP vs Data Warehousing

Databases – What is ACID?

What does ACID mean in database technologies? Concerning databases, the acronym ACID means: Atomicity, Consistency, Isolation, and Durability. Why is ACID important? Atomicity, Consistency, Isolation, and Durability (ACID) are import to database, because ACID is a set of properties that guarantee that database transactions are processed reliably. Where is the ACID Concept described? Originally described … Continue reading Databases – What is ACID?

Databases – Database Isolation Level Cross Reference

  Here is a table quick reference of some common database and/or connection types, which use connection level isolation and the equivalent isolation levels. This quick reference may prove useful as a job aid reference, when working with and making decisions about isolation level usage. Database isolation levels Data sources Most restrictive isolation level More … Continue reading Databases – Database Isolation Level Cross Reference

Database – 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 … Continue reading Database – What is a foreign key?

Database – What is a Composite Primary Key?

Database Table What is a Composite Primary Key? A Composite Primary key is Primary key What a primary key, which is defined by having multiple fields (columns) in it.  Like a Primary Key what a composite Primary Key is depends on the database.  Essentially a Composite Primary Key: Is a combination of Fields (columns) which … Continue reading Database – What is a Composite Primary Key?

Database – What is a Primary Key?

Database Table What is a primary Key? What a primary key is depends, somewhat, on the database.  However, in its simplest form a primary key: Is a field (Column) or combination of Fields (columns) which uniquely identifies every row.Is an index in database systems which use indexes for optimizationIs a type of table constraintIs applied … Continue reading Database – What is a Primary Key?

Database – What is DDL?

SQL (Structured Query Language) What is DDL (Data Definition Language)? DDL (Data Definition Language), are the statements used to manage tables, schemas, domains, indexes, views, and privileges.  The the major actions performed by DDL commands are: create, alter, drop, grant, and revoke. Related References What is DCL?What is DML?Database Table Field Ordering Effective PracticesStructured Query Language … Continue reading Database – What is DDL?