Table:
0
A
B
C
D
E
1
id
user id
text
create date
tweets
2
1
1
Hello I'm Tony Stark.
2018-03-09 20:00:14
3
2
3
Today I have went shopping at Laffayette.
2018-03-09 20:01:02
4
4
1
My company is hiring interns.
2018-03-12 02:30:30
5
5
4
Oh, I only have a few fans.
2018-03-12 02:30:30
6
6
6
Let’s celebrate women, fight for equality and support each other,  not just today, but everyday!
2018-03-12 02:30:30
7
7
5
I love my new boyfriend.
2018-03-12 02:30:30
8
8
4
I feel tired and don't want to write SQLs.
2018-03-12 02:30:30
9
9
6
I had a pretty rough time during the last couple of weeks
2018-03-12 02:30:30

Questions and formulas:
Question: Find the number of tweets in record.
Formula: ROWS(UNIQUE(E1))
Formula2: ROWS(UNIQUE(E2:E9))
Level: easy
Question: Find the number of users who posted some tweets.
Formula: ROWS(UNIQUE(B1))
Formula2: ROWS(UNIQUE(B2:B9))
Level: easy
Question: Return the text of tweets about the topic 'intern'.
Formula: FILTER(C1,IFERROR(SEARCH("intern",C1),0))
Formula2: FILTER(C2:C9,IFERROR(SEARCH("intern",C2:C9),0))
Level: medium
Question: How many tweets?
Formula: ROWS(UNIQUE(E1))
Formula2: ROWS(UNIQUE(E2:E9))
Level: easy
Question: How many users posted tweets?
Formula: SUMMARIZE(E1,SUMX(B1))
Formula2: SUMMARIZE(E2:E9,SUMX(B2:B9))
Level: easy
Question: Show all texts and tweets 
Formula: UNIQUE(HSTACK(C1,E1))
Formula2: UNIQUE(HSTACK(C2:C9,E2:E9))
Level: easy
Question: What are the text and tweets?
Formula: UNIQUE(HSTACK(C1,E1))
Formula2: UNIQUE(HSTACK(C2:C9,E2:E9))
Level: easy