How to Fix 'Unknown Column in Field List' Error in Spring Boot JPA

What does the 'unknown column in field list' error mean in Spring Boot JPA?

// Example JPA Entity
@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "username")
    private String username;

    // getters and setters
}

The 'unknown column in field list' error in Spring Boot JPA typically occurs when the query you execute is referencing a column that does not exist in the database table. This is often the result of discrepancies between your Java entity configuration and the actual database schema.

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "username")
    private String username; // Ensure 'username' column exists in the 'users' table

    // getters and setters
  
   // For Example, ensure that your SQL table create statement matches:
   // CREATE TABLE users (id BIGINT AUTO_INCREMENT, username VARCHAR(255), PRIMARY KEY (id));
}

Causes

• The database table does not contain the specified column name.
• Mismatched database schema due to recent changes that have not been migrated.
• Typographical errors in the property names of the JPA entity or in the database column names.
• Case sensitivity in column names between the database and the Java entity.

Solutions

• Verify that the column names in your entity match those in the corresponding database table.
• Update your database schema to include the missing column if it was omitted during migrations.
• Ensure that your application is configured to connect to the correct database by checking the application.properties or application.yml.
• Check for typos in the `@Column` annotation or corresponding database table definitions.

Mistake: Assuming database column names are case insensitive.

Solution: Always check the case of your SQL column names as most databases are case-sensitive.

Mistake: Not updating the database schema after making changes to the JPA entities.

Solution: Run migrations or scripts to ensure that the database schema is in sync with your entity definitions.

Mistake: Using incorrect or inconsistent property names in entity configuration compared to the database schema.

Solution: Use the `@Column(name = "db_column_name")` annotation to explicitly define the mapping if necessary.