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What is the definition of a foreign key?


A foreign key is a table that can be linked to another table's primary key. By referencing a foreign key with the primary key of another database, a relationship between two tables must be established.
 

What exactly is a join?


This term is used to query data from many tables depending on the tables' fields' relationships. When using JOINs, keys are quite important.
 

What are the different types of joins and how do you explain them?



There are several sorts of joins that can be used to extract data, depending on the tables' relationships.
  • Joining from the inside.
When there is at least one row match between the tables, the inner join returns rows.
  • Join to the right.
The right join returns all rows of the right hand side table as well as rows that are common between the tables. Simply put, it returns all of the rows from the right-hand side table, even if the left-hand side table has no matches.
  • Join from the left.
Rows that are common between the tables and all rows of the Left hand side table are returned by the left join. Simply put, even if there are no matches in the Right hand side table, it returns all the rows from the Left hand side table
  • Full Participation.
When there are matching rows in any of the tables, a full join returns rows. This means it retrieves all rows from both the left and right side tables. Check SQL INTERVIEW QUESTIONS - Tips For Perfect Interview!
 

What is the definition of normalization?


Normalization is the process of structuring a database's columns and tables to reduce redundancy and dependency. The primary goal of normalization is to add, delete, or edit fields in a single table.
 

What is Denormalization and How Does It Work?


DeNormalization is a database access technique that converts data from higher to lower normal forms. It's also the technique of combining data from related tables into a table to add redundancy.
 

What is a Point of View?


A view is a virtual table that represents a portion of the data in a database. There are no simulated views, and it takes up less storage space. The data from one or more tables can be integrated in a view, depending on the relationship.
 

What is the definition of an index?


An index is a performance tuning method for retrieving records from a table more quickly. An index establishes an entry for each value, making data retrieval faster.
 

What are the various kinds of indexes?


There are three different sorts of indexes:

Index that is unique.

If the column is unique indexed, this indexing prevents duplicate values in the field. When a primary key is defined, a unique index can be applied automatically.

Clustered Index is a type of index.

This index reorders the table's physical order and allows for searches based on key values. There can only be one clustered index per table.

Index that is not clustered.

NonClustered Indexes do not change the physical order of the table and keep the data in its logical order. There are a maximum of 999 nonclustered indexes per table.


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