❌ 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 TypeMeaningDetected When
Syntax ErrorWrong SQL grammar or structureAt query execution
Logical ErrorQuery runs but gives wrong resultAfter seeing output
Runtime ErrorError occurs while query is runningDuring execution
Constraint ErrorViolation of table rulesAt data insert/update
Semantic ErrorCorrect syntax but wrong meaningAt 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;

✔ 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;

✔ 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.

✔ Check table structure before writing queries.

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