Top 52 SQL Interview Questions
Define a temp table
What is PRIMARY KEY?
PRIMARY KEY?What is a VIEW?
VIEW?What is DEFAULT?
DEFAULT?What is FOREIGN KEY?
FOREIGN KEY?What is the difference between Data Definition Language (DDL) and Data Manipulation Language (DML)?
What is the difference between WHERE clause and HAVING clause?
WHERE clause and HAVING clause?
Mid Mid How does a Hash index work?
Mid What is the difference between INNER JOIN and OUTER JOIN?
INNER JOIN and OUTER JOIN? Mid What is Collation?
Mid Mid Mid What is the difference between INNER JOIN, OUTER JOIN, FULL OUTER JOIN?
INNER JOIN, OUTER JOIN, FULL OUTER JOIN? Mid What is the difference between JOIN and UNION?
JOIN and UNION? Mid Discuss INNER JOIN ON vs WHERE clause (with multiple FROM tables)
INNER JOIN ON vs WHERE clause (with multiple FROM tables) Mid Describe the difference between truncate and delete
Mid Mid What is the difference between UNION and UNION ALL?
UNION and UNION ALL? Mid Mid Mid Senior Senior What is an execution plan, and how do you use it to optimize a slow query?
Senior Senior Senior Senior What is the difference among UNION, MINUS and INTERSECT?
UNION, MINUS and INTERSECT? Senior Expert Expert Expert Expert Expert What is a Common Table Expression (WITH / CTE), and when would you use it?
WITH / CTE), and when would you use it?
Junior Rising Temperature Challenge
Junior How to select first 5 records from a table?
5 records from a table? Mid Duplicate Emails Challenge
Mid How would you find the second highest salary in a table?
Mid What is the difference between EXISTS and IN?
EXISTS and IN? Mid What is the difference between ROW_NUMBER(), RANK(), and DENSE_RANK()?
ROW_NUMBER(), RANK(), and DENSE_RANK()? Mid Mid How can we transpose a table using SQL (changing rows to column or vice-versa)?
Senior How to generate row number in SQL without ROWNUM
ROWNUM Senior Department Highest Salary Challenge
Senior Trips and Users Challenge
Senior What would happen without an Index?
Senior Senior Delete duplicate values in a SQL table
Senior How can I do an UPDATE statement with JOIN in SQL?
UPDATE statement with JOIN in SQL? Senior Select first row in each GROUP BY group (greatest-n-per-group problem)?
GROUP BY group (greatest-n-per-group problem)? Expert 
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