Data modeling interview questions

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1). What is a Data Model?

A Data Model is the conceptual representation of business requirements or physical attributes of a database that are actually helpful in communicating the business requirements with clients.

2). How can you define the data modeling?

The approach that is used to prepare a data model is called the Data Modeling.

3). Name the possible type of a Data Model.

It could be physical data model and the logical data model, enterprise data model, conceptual data model, relational data model, OLTP data model etc.

[ Related Article – How ETL acts as an intermediate between OLTP and OLAP? ]

 

4). What is contained by the physical data model?

A physical data model contains Table, key constraints, columns, unique key, Foreign Key, default values, indexes etc.

5). What is contained by the logical data model?

A logical data model contains entity, attributes, primary key, alternate key, Inversion keys, rule, definition, business relation etc.

6). How will you differentiate physical data model from physical data modeling?

A physical data model contains the physical attributes of a database. The database performance, physical storage, and the indexing strategy are the important considerations of a physical data model. The main component here is a database. The approach that is used for creating a physical data model is called the physical data modeling.

7). How will you differentiate logical data model from logical data modeling?

A logical data model is related to the business requirements and it is used for actual implementation of the data. The approach that is used for creating a logical data model is called the logical data modeling.

8). What is an entity (Table)?

A database is consisting of multiple rows and columns which is called as table together. Further, each column has a specific datatype and based on conditions constraints are set of the columns.

9). What is an attribute (Column)?

A Column is defined as the vertical alignment of data and information stored for that particular column.

10). What is a row?

A row is the set of tuples, records, or it could be taken as the horizontal arrangement of the data.

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11). How can you define the ERD (Entity Relationship Diagram)?

ERD is a logical representation of entities and defining the relationship among entities. Entities are given in boxes and the relationships are given by arrows.

12). What do you understand by the primary key constraint in a database?

The primary key constraint is set on a column to avoid null values or duplicate values. In simple words, a column containing unique items throughout can be defined as the primary key constraint. It could be the bank number, security number or more.

13). What do you understand by the composite primary key constraint?

When more than a single column can be defined as the primary key constraint, it becomes composite.

14). What do you know about foreign key constraint?

The Primary key can be defined for the parent table and foreign key is set for the child table. The foreign key constraint always refers to the primary key constraint in the main table.

15). Tell us something about the surrogate key.

When a numerical attribute is enforced on a primary key in a table, it is called the surrogate key. This could be defined as the substitute for natural keys. Instead of generating primary or foreign keys, surrogate keys are generated by the database and they are further helpful in designing the SQL queries.

16). Why composite word is added before any key constraint?

When the same constraint is enforced on multiple columns then the composite word is added before that particular key constraint.

17). Name a few popular relationships within a data model.

These are identifying, non-identifying, and self-recursive relationships in a data model.

18). What do you mean by the identifying relationships in a data model?

As you know the parent table and the child table both are connected together with a thin line. When the referenced column in a child table is a part of the primary key in the parent table then those relationship is drawn by a thick line and it is named as the identifying relationships in a data model.

19). Is there exists any non-identifying relationship too?

In most of the cases, a parent table and the child table both are connected together with a thin line. When the referenced column in a child table is not a part of the primary key in the parent table then those relationship is drawn by a dotted line and it is named as the non-identifying relationships in a data model.

20). How will you define the cardinality in a data model?

Cardinalities are used to define relationships and it could be one-to-one, one-to-many, or many-to-many etc. Higher the value of cardinality, there will be more unique values within a column.

21). What do you mean by the self-recursive relationships?

This is a standalone column in the table that is connected to the primary key of the same table and named as the self-recursive relationship here.

22). Give a quick definition to the enterprise data model.

Here, all important entities are defined related to an enterprise. You should understand the basic data elements first and the possible relationship between them. This relationship is defined as the enterprise data modeling. To understand this model in the best areas, you should divide the data models into subject areas.

23). How will define the relational data model?

The visual representation of data objects within a database is named as the relational data model. The approach used to create a relational data model is called the relational data modeling.

24). What is OLTP data modeling?

OLTP or Online Transaction Processing is an approach where the data model is specially created for the transactions and the approach is named as the OLTP data modeling.

25). What is conceptual data modeling?

It will give you a detailed level of information related to the entity, attributes, or relationships existing between them.

26). What is a constraint? Why constraints are important for a database?

This is a rule imposed on the data. A different type of constraints could be unique, null values, foreign keys, composite key or check constraint etc.

27). Define unique constraint for a database.

This constraint is added to avoid duplicate values within a column.

28). Define the check constraint.

A check constraint is useful to define the range of values within a column.

29). What is an index in a database?

An Index is composed of a set of columns or a single column that is needed for fast retrieval of data.

30). What is the sequence?

A sequence could be defined as the database object that is needed for the creation of the unique number.

31). How will you define the database normalization?

To simplify the data based on standard rules, database normalization is needed.

——Best of Luck——

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