Infogain Interview Questions and Answers

50% increase in female population contributed more to the overall population increase in the village.

• Calculate the actual increase in male and female population separately.

• Compare the percentage increase in male and female population.

• The group with the higher percentage increase contributed more to the overall population increase.

Primary key uniquely identifies each record in a table, while foreign key establishes a link between two tables.

• Primary key ensures each record is unique

• Foreign key establishes a relationship between tables

• Primary key can be a single column or a combination of columns

• Foreign key references the primary key of another table

When creating a table, factors to consider include data types, column names, primary keys, relationships, and constraints.

• Consider the data types for each column (e.g. integer, text, date)

• Choose appropriate column names that are descriptive and easy to understand

• Define primary keys to uniquely identify each row

• Establish relationships between tables using foreign keys

• Set constraints to enforce data integrity (e.g. unique, not null)

WHERE is used to filter rows before grouping, HAVING is used to filter groups after grouping.

• WHERE is used with SELECT statement to filter rows based on a condition

• HAVING is used with GROUP BY statement to filter groups based on a condition

• WHERE is applied before grouping, HAVING is applied after grouping

• Example: SELECT * FROM table_name WHERE column_name = 'value'

• Example: SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name HAVING COUNT(*) > 1

Delete removes rows one by one, while truncate removes all rows at once.

• Delete is a DML command, while truncate is a DDL command

• Delete can be rolled back, while truncate cannot be rolled back

• Delete triggers delete triggers, while truncate does not trigger any triggers

• Delete is slower than truncate for large tables

• Example: DELETE FROM table_name WHERE condition;

• Example: TRUNCATE TABLE table_name;