DataBeat Interview Questions and Answers

Q1. SQL advanced questions
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Q2. Dataa visualizns
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Sql concepts and sql Queries

Q1. Difference between where and having
Ans. 
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 G
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Q2. Difference between delete and truncate
Ans. 
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;
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Q3. What is primary key and foreign key
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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
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Q4. Query Execution order
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Q5. What we consider for creating table
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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. uniqu
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Q1. Explain about joins?
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Joins are used in databases to combine rows from two or more tables based on a related column between them.
• Joins are used to retrieve data from multiple tables in a single query.

• Common types of joins include inner join, left join, right join, and full outer join.

• Inner join returns only the matching rows between the tables.

• Left join returns all rows from the left table and the matching rows from the right table.

• Right jo...read more
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