In DBMS, NULL represents a missing, unknown, or inapplicable value in a database field.
It does NOT mean:
Zero (
0)Empty string (
"")False
It simply means:
🔹 "No value has been assigned" or
🔹 "Value is not known at the moment"
📦 Real-Life Examples:
Student_ID | Name | Age | |
|---|---|---|---|
101 | Swastika | 19 | |
102 | Aisha | 20 | NULL |
103 | Rahul | NULL |
For Aisha,
Emailis NULL — she didn’t provide it.For Rahul,
Ageis NULL — we don’t know his age yet.
⚠️ Important Properties of NULL:
Property | Description |
|---|---|
NULL ≠ 0 | NULL is not zero. Zero is a known value; NULL means no value. |
NULL ≠ '' (empty string) | NULL is not an empty string. An empty string is still a value. |
NULL ≠ NULL | In SQL, NULL is not equal to NULL — you must use |
Arithmetic with NULL | Any math operation with NULL gives NULL. Ex: |
🧠 Summary:
🔸 Term | 📖 Meaning |
|---|---|
| Unknown / missing / inapplicable value |
Not same as |
|
Use in SQL |
|