✘ Types of Errors in SQL

Last Updated: 7th January 2026

While writing SQL queries, errors are very common—especially.Understanding types of SQL errors helps you identify problems quickly and fix them correctly.

An SQL error occurs when a query:

Breaks SQL syntax rules
Refers to invalid database objects
Violates database constraints
Uses incorrect logic

When an error occurs, the database engine returns an error message.

🗂️ Main Types of SQL Errors

Error Type	Meaning	Detected When
Syntax Error	Wrong SQL grammar or structure	At query execution
Logical Error	Query runs but gives wrong result	After seeing output
Runtime Error	Error occurs while query is running	During execution
Constraint Error	Violation of table rules	At data insert/update
Semantic Error	Correct syntax but wrong meaning	At execution

Syntax Errors

A Syntax Error happens when SQL grammar rules are violated.

Common Causes

Misspelled SQL keywords
Missing commas or parentheses
Incorrect clause order

Example

SELEC * FROM students;

✘ SELEC is incorrect

SELECT * FROM students;

$\checkmark$ Correct:

Logical Errors

A Logical Error means:

Query runs successfully
Output is not what you intended

Wanted students with marks greater than or equal to 90, this query is logically incorrect.

Example

SELECT * FROM students WHERE marks > 90;

SELECT * FROM students WHERE marks >= 90;

$\checkmark$ Correct:

Hinglish Tip 🗣: Logical error me query galat nahi hoti, soch galat hoti hai.

Runtime Errors

A Runtime Error occurs while the query is executing.

Common Causes

Division by zero
Invalid type conversion
Missing required values

Example

SELECT 10 / 0;

✘ Division by zero causes a runtime error.

Constraint Errors

A Constraint Error occurs when database rules are violated.

Common Constraints

PRIMARY KEY
UNIQUE
NOT NULL
FOREIGN KEY
CHECK

Example

INSERT INTO students (id, name)
VALUES (1, 'Amit');

If id = 1 already exists and id is a primary key → error occurs.

Semantic Errors

A Semantic Error happens when:

Syntax is correct
Query refers to invalid or non-existing objects

Example

SELECT age FROM students;

If the age column does not exist, the query fails.

$\checkmark$ Check table structure before writing queries.

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