Pharmarack Technologies Interview Questions, Process, and Tips

Types of Joins are used in SQL to combine rows from two or more tables based on a related column between them.

• Inner Join: Returns only the matching rows from both tables.

• Left Join: Returns all the rows from the left table and the matching rows from the right table.

• Right Join: Returns all the rows from the right table and the matching rows from the left table.

• Full Outer Join: Returns all the rows from both tables, inclu...read more

Drop command removes a table from the database while delete command removes rows from a table.

• Drop command is a DDL (Data Definition Language) command while delete command is a DML (Data Manipulation Language) command.

• Drop command is irreversible and removes the entire table structure and its data while delete command only removes specific rows.

• Drop command requires the DROP privilege while delete command requires the ...read more

Primary key uniquely identifies each record in a database table.

• Primary key ensures data integrity and consistency.

• It helps in faster data retrieval and indexing.

• It can be a single column or a combination of columns.

• Primary key cannot have null values.

• Examples of primary keys are social security number, email address, etc.

A foreign key is a column or set of columns in a table that refers to the primary key of another table.

• It is used to establish a relationship between two tables in a database.

• It ensures referential integrity by preventing invalid data from being inserted into the table.

• It allows for efficient querying and joining of related data.

• Example: A customer table may have a foreign key that references the primary key of an orde...read more

Query to display employees records

• Use SELECT statement to retrieve data from employee table

• Specify the columns to be displayed in the SELECT statement

• Use WHERE clause to filter the records based on specific conditions

• Use ORDER BY clause to sort the records in ascending or descending order