Thread by @swapnakpanda

SQL Interview Questions (S2)

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This is the 2nd in this series. Check the first one 👇

https://twitter.com/swapnakpanda/status/1455768957374242817?s=20

Disclaimer:

• The questions covered here are mostly conceptual
• I never claim during interviews, only these type of questions are/should be asked
• For interviews, you should have fundamentals strong. And you should be able to provide solutions to practical problems.

Series: 2️⃣
Level: Beginner
Topics:

1️⃣ Data Types
2️⃣ Operators
3️⃣ Functions
4️⃣ Views
5️⃣ Aggregation

1️⃣ Data Types

* Data Types vary across SQL Vendors like Oracle, MySQL etc. So questions are specific to particular vendors.

✪ When do you define data type of a column?
✪ Can a data type be changed later? What are the restrictions?

✪ What are different numeric data types?
✪ What data type is used to store a boolean?
✪ What data type is used to store bits?
✪ What data type is used for integers?
✪ What data type is used for floating point numbers?

✪ What are different String data types?
✪ What data type is used to store binary data?
✪ What is the difference between CHAR, VARCHAR and VARCHAR2 (Oracle)?
✪ What is a Large Object Data Type?
✪ What are different Large Object Data Types?

✪ What is the difference between BLOB and CLOB?
✪ When should you go for a large object data type instead of a String data type?
✪ What are different Date/Time Data Types?

2️⃣ Operators

✪ What operator to use to verify if all subqueries meet the condition?
✪ What operator to use to verify if any of the subqueries meet the condition?
✪ What operator to use to check if operand is within a range?

✪ What operator to use to check if operand should one of the given values.
✪ What operator to use to check if a subquery returns at least one record?
✪ What operator to use to check if operand matches a pattern?
✪ What is the difference between BETWEEN and IN operators?

✪ What is the difference between = and LIKE operator?
✪ How to check if a field is containing a NULL value?
✪ What are different comparison operators?
✪ What is the operator to check for not equality?

3️⃣ Functions

✪ What is a SQL function?
✪ What function to use to return current system date and time?
✪ What function to use to find length of a text field?
✪ What function to use to convert a text field to upper/lower case?

✪ How to get a substring?
✪ What are different format options to display a text field?
✪ How to round a numeric field to certain precision?
✪ Give examples of some Date/Time functions?
✪ How to get the year/month/date from a Date field?
✪ How to get last day of the month?

4️⃣ Views

✪ What is a View?
✪ How is a View different from a Table?
✪ What are various use cases of a View?
✪ Can a View be used to insert/delete records?
✪ How to create/update a View?
✪ What is "WITH CHECK OPTIONS"?
✪ What is a Materialised View? Difference with a View?

5️⃣ Aggregation

✪ What do you mean by aggregation?
✪ What is the difference between aggregation and projection?
✪ What does "GROUP BY" statement do?
✪ What is the difference between WHERE and HAVING?
✪ Is "ORDER BY" an aggregation statement?

✪ What function to use to find number of records?
✪ What function to use fetch the first/last value for a field?
✪ What function to use to fetch max/min/average value of a field?
✪ What function to use to find summation of all values for a field?

The next 🧵 of this series will provide questions from

1️⃣ More on DDL
2️⃣ More on DML
3️⃣ Index
4️⃣ Sequence
5️⃣ Trigger

Check 👇 for "Interview Questions" on few other subjects.

https://twitter.com/swapnakpanda/status/1456599023704436744?s=20