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MySQL COALESCE
MySQL COALESCE() Function
The COALESCE() function in MySQL returns the first non-NULL value from a list of values. It is a helpful function when working with nullable fields and ensures meaningful output instead of NULL.
COALESCE() Example
students Table
student_id |
name |
gender |
city |
age |
score |
course_id |
phone_number |
|
|---|---|---|---|---|---|---|---|---|
1 |
Alice |
Female |
Delhi |
20 |
85 |
101 |
NULL |
1234567890 |
2 |
Bob |
Male |
Mumbai |
22 |
75 |
NULL |
bob@email.com |
NULL |
3 |
Charlie |
Male |
Delhi |
21 |
95 |
102 |
NULL |
NULL |
4 |
David |
Male |
Bangalore |
23 |
65 |
101 |
david@email.com |
NULL |
5 |
Eve |
Female |
Mumbai |
20 |
80 |
103 |
NULL |
NULL |
6 |
Frank |
Male |
Delhi |
22 |
90 |
103 |
NULL |
NULL |
7 |
Alice |
Female |
Mumbai |
19 |
60 |
102 |
NULL |
NULL |
The following SQL statement used to display the preferred contact information (Email first, then Phone if Email is NULL).
Output:
name |
preferred_contact |
|---|---|
Alice |
1234567890 |
Bob |
|
Charlie |
No Contact Available |
David |
david@email.com |
Eve |
No Contact Available |
Frank |
No Contact Available |
Alice |
No Contact Available |
Explanation:
- If email is NULL, it uses phone_number.
- If both are NULL, it returns
"No Contact Available".