Top 50 SQL Interview Questions (2026)
Ranked by how often they come up. Every question has a complete worked answer, runnable code and follow-ups — free to read.
50 questions15 Easy24 Tricky10 Medium1 Hard
- 1
What is SQL?
Easy - 2
Types of SQL Commands
Easy - 3
DDL vs DML vs DCL vs TCL
Easy - 4
Primary Key
Easy - 5
Foreign Key
Easy - 6
Candidate Key
Tricky - 7
Composite Key
Medium - 8
Super Key
Easy - 9
Alternate Key
Tricky - 10
Unique Key
Medium - 11
NOT NULL
Easy - 12
CHECK Constraint
Easy - 13
DEFAULT Constraint
Easy - 14
AUTO_INCREMENT / IDENTITY
Tricky - 15
CREATE
Easy - 16
ALTER
Medium - 17
DROP
Tricky - 18
TRUNCATE
Tricky - 19
DELETE
Easy - 20
DELETE vs TRUNCATE vs DROP
Tricky - 21
SELECT
Easy - 22
DISTINCT
Tricky - 23
WHERE
Easy - 24
ORDER BY
Easy - 25
LIMIT
Medium - 26
OFFSET
Tricky - 27
TOP
Tricky - 28
LIKE
Tricky - 29
IN
Tricky - 30
BETWEEN
Tricky - 31
EXISTS
Tricky - 32
NOT EXISTS
Tricky - 33
ANY
Tricky - 34
ALL
Tricky - 35
CASE
Tricky - 36
COALESCE
Tricky - 37
NULL Handling
Tricky - 38
Aliases
Tricky - 39
CAST
Medium - 40
Date Functions
Medium - 41
INNER JOIN
Easy - 42
LEFT JOIN
Medium - 43
RIGHT JOIN
Medium - 44
FULL OUTER JOIN
Tricky - 45
CROSS JOIN
Tricky - 46
SELF JOIN
Medium - 47
NATURAL JOIN
Tricky - 48
Join Order
Tricky - 49
Nested Loop Join
Medium - 50
Hash Join
Hard
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