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SQL NULL handling — practice questions · JobPrax
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All SQL topics
SQL
NULL handling
IS NULL, COALESCE, NULLIF and NULLs in aggregates.
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All levels
Basic (26)
Intermediate (7)
Advanced (7)
All
To do
Solved
1
Find missing values
Basic
2
Has a value
Basic
3
Replace with COALESCE
Basic
4
Missing manager
Basic
5
NULL in arithmetic
Basic
6
Unknown department
Basic
7
No email
Basic
8
Has a phone
Basic
9
Count missing phones
Basic
10
Fill in a default
Basic
11
No department
Basic
12
Projects still open
Basic
13
Planned end date
Basic
14
Rows vs filled values
Basic
15
Came on their own
Basic
16
Fees still due
Basic
17
The missing mark
Basic
18
Missing counts as zero
Basic
19
Email or a note
Basic
20
Unassigned department
Basic
21
Referred or not
Basic
22
The top boss
Basic
23
Averages skip NULLs
Basic
24
Zero becomes empty
Basic
25
Paid date or pending
Basic
26
Fully filled customers
Basic
27
NULLs and aggregates
Intermediate
28
Treat missing as zero in an average
Intermediate
29
NULLIF to avoid divide by zero
Intermediate
30
NOT IN trap
Interview
Intermediate
31
Referred vs organic
Intermediate
32
First available contact
Intermediate
33
NULLs sort where?
Intermediate
34
Comparing possibly-NULL columns
Advanced
35
Fill gaps with the previous value
Interview
Advanced
36
Data completeness report
Advanced
37
NULL-safe join
Advanced
38
Customers missing any contact
Advanced
39
Unpaid fee totals
Advanced
40
Most recent non-null email
Advanced