SQL Server engine errors
SQL Server 515 Cannot Insert NULL
Cannot Insert NULL — a required column does not allow null values
What 515 Means
The 515 error on the SQL Server engine errors indicates cannot insert null — a required column does not allow null values. This typically occurs due to an insert statement omits a not null column that has no default value.
Error 515 fires when an INSERT or UPDATE operation attempts to assign NULL to a column defined as NOT NULL with no default constraint. It is one of the most common data integrity errors in SQL Server.
Technical Background
Error 515 is a constraint enforcement error at the column level. It differs from error 547 (foreign key / check constraint violation) in that 515 specifically enforces the NOT NULL property. The error message names the exact table and column where the null was rejected.
In many applications, this error indicates a mismatch between the application's data model and the database schema. Adding a DEFAULT constraint to the column or validating input before the INSERT are the two standard approaches to prevent it.
Common Causes
- An INSERT statement omits a NOT NULL column that has no default value
- Application code passes null for a field the database schema requires
- A data migration script maps a source column with nulls to a target column that forbids them
Typical Scenarios
- A web form submission leaves a required field blank and the ORM sends NULL to the database
- An ETL job encounters source rows with missing values for a mandatory target column
What to Know
The error message identifies the specific table and column that rejected the null value. Resolving the mismatch between the application's data expectations and the database schema's constraints is the core task.
Frequently Asked Questions
Common questions about SQL Server 515 error
By default, only the individual statement fails. The transaction remains open unless the application explicitly rolls it back or SET XACT_ABORT is ON.