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TOP 10 SQL Concepts for Job Interview

1. JOINs (Inner/Left/Right/Self)
2. Group By and Order By
3. Aggregate Functions (sum/avg/max/min)
4. Union and Union All
5. Date and Time processing
6. String processing
7. Window Functions (Partition by)
8. Subquery
9. View and Index
10. Common Table Expression (CTE)

SQL Join is a very important concept for any Data Science or Analytics Job Interview as well as day to day work.

Please refer to this 3 page document for understanding different SQL Join types.

Once you have understood the concepts, please go ahead and practise it with some actual or sample data tables.

(Document Credit: Steve Stedman)

I’m sure SQL will help you a lot in your Data Science journey and make you an awesome Data Scientist. All the best! πŸ‘πŸ»

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import java.util.PriorityQueue;
public class Main
{
public static void main(String[] args) {
PriorityQueue<Integer> p=new PriorityQueue<Integer>();
p.add(1);
p.add(2);
p.add(3);
System.out.println(p.poll());
System.out.println(p.offer(4));
p.add(1);
p.remove(2);
System.out.println(p.peek());
System.out.println(p);
}
}
Which allows the removal of elements from a collection?
Anonymous Quiz
27%
Enumeration
37%
Iterator
28%
Both
8%
None
The Comparator interface contains the method?
Anonymous Quiz
15%
compareWith()
61%
compareTo()
24%
compare()
Which of these is synchronized?
Anonymous Quiz
12%
TreeMap
23%
HashMap
28%
Hashtable
37%
All
Which is more offers best performance?
Anonymous Quiz
12%
TreeMap
27%
HashMap
30%
LinkedHashMap
30%
All are equal
Which of these class should be preferred to be used as a key in a HashMap?
Anonymous Quiz
21%
String
41%
Integer
8%
Double
29%
Any of these
What should we use when add and remove operations are more frequent than get operations?
Anonymous Quiz
37%
LinkedList
27%
ArrayList
10%
Vector
27%
All
Iterator returned by ArrayList is?
Anonymous Quiz
56%
Fail-fast
33%
Fail-safe
11%
none
Iterator returned by LinkedList is?
Anonymous Quiz
38%
Fail-fast
53%
Fail-safe
9%
none
Iterator returned by CopyOnWriteArrayList is ?
Anonymous Quiz
50%
Fail-fast
41%
Fail-safe
9%
none
Iterator returned by HashMap on key, value and entry is?
Anonymous Quiz
48%
Fail-fast
43%
Fail-safe
9%
none
Iterator returned by Hashtable on key, value and entry is?
Anonymous Quiz
63%
Fail-fast
29%
Fail-safe
8%
None