Interview BD

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Therap Database Engineer ​

Interview Stages ​

The selection process has 4 stages,

  1. Initial screening: This round is taken in written format
  2. 1st technical round The first round is taken by the BD team
  3. 2nd technical round: This round is typically taken by both USA and BD team. However, the final selection is done by the US team.
  4. HR Round: This is the final stage before onboarding and typically deals with salary negotiation.

Database Questions ​

Design an ERD of online restaurant management system

What is Database Transaction

Briefly explain ACID properties

Show Answer

ACID is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. Databases that support this are called ACID compliance. The properties are

  • Atomicity: Each statement in a transaction (to read, write, update or delete data) is treated as a single unit. Either the entire statement is executed, or none of it is executed.
  • Consistency: Ensures the databases remain consistent following some predefined business logic both before and after the transaction
  • Isolation: Each transaction executes in such a way that one is not affected by other s though they were occurring only one.
  • Durability: The data changes by a successfull transaction is saved even in the event of system failure

IMPORTANT

Atomicity, isolation and durability are properties of the database, whereas consistency is a property of the application. The C in ACID was tossed in to make the acronym work. [ref: Martin Kleppmann, Designing Data Intensive Applications]

What is normalization and denormalization

Briefly explain BCNF

Explain data warehousing

Explain data redundancy

Briefly mention the differences between stored procedure, function and trigger

Briefly mention the differences between delete, drop and truncate

Briefly mention the differences between where and having clause

Briefly mention the differences between candidate key and super key

A schema has entities like CUSTOMERS, ORDERS, ORDER_ITEMS, PRODUCTS, PRODUCT_DETAILS, WAREHOUSES, INVENTORIES. Data fields of entities and cardinality relationships were given in the figure. Questions included from <>

  1. Group by, Order by, Join <>
  2. Extracting month and year from oracle dates <>
  3. Find ranks based on some criterion. The extremely hard question was - find top 10 customers based on their total amount spent in 2023. This one involved the following topics: aggregation, join of multiple tables, nested sub-query, year extraction from date. The book of Sukarna sir contains one/two such exercises. Practise them properly