SQL Server Error 1919

Error number

1919

Severity

16 (user-correctable error)

State

1

Product

Microsoft SQL Server Database Engine

Versions

All supported SQL Server versions (2016 to 2025), Azure SQL Database, Azure SQL Managed Instance

Category

Syntax & Object Resolution

Last reviewed

24 October 2026

What it means

Error 1919 means you tried to use a large-value column (varchar(max), nvarchar(max), varbinary(max), text, ntext or image) as an index key, which SQL Server does not allow.

Index keys are stored in sorted order in every level of the index, so each key must fit within a fixed limit (900 bytes for a clustered index, 1,700 bytes for a nonclustered index). Large-value types can hold up to 2 GB per value, so SQL Server refuses them as key columns before it looks at any data, even when the table is empty. The message names the column and the table: check that column's data type.

The same rule applies to the hidden index behind a PRIMARY KEY or UNIQUE constraint, which is why a CREATE TABLE or ALTER TABLE ... ADD CONSTRAINT can fail with 1919 followed by 1750 ("Could not create constraint or index"). Large-value columns are still allowed in an index as included (non-key) columns, which is the basis of most fixes.

Common causes

• A column declared as nvarchar(max) or varchar(max) by default (often by an ORM or a migration tool) and then used in CREATE INDEX.
• A PRIMARY KEY or UNIQUE constraint on a (max) column, such as an e-mail address, URL or hash stored as varchar(max) or varbinary(max).
• Legacy text, ntext or image columns in a key.
• An index script copied from another database where the column had a shorter type.

Diagnose it

Read-only These queries only read metadata and dynamic management views. They do not change data, permissions or configuration, so they are safe to run first.

SELECT c.name AS column_name, t.name AS type_name, c.max_length
FROM sys.columns AS c
JOIN sys.types AS t ON t.user_type_id = c.user_type_id
WHERE c.object_id = OBJECT_ID(N'dbo.Articles')
  AND (c.max_length = -1 OR t.name IN (N'text', N'ntext', N'image', N'xml'))
ORDER BY c.column_id;

SELECT MAX(LEN(title)) AS longest_chars,
       MAX(DATALENGTH(title)) AS longest_bytes,
       COUNT(*) AS total_rows
FROM dbo.Articles;

How to fix it

Each fix is labelled with what it changes. Try read-only checks and the least invasive fix first, and test changes outside production.

ALTER TABLE dbo.Articles ALTER COLUMN title NVARCHAR(450) NULL;
CREATE INDEX IX_Articles_title ON dbo.Articles (title);

ALTER TABLE dbo.Articles
    ADD title_hash AS CAST(HASHBYTES('SHA2_256', title) AS BINARY(32)) PERSISTED;
CREATE INDEX IX_Articles_title_hash ON dbo.Articles (title_hash) INCLUDE (title);

SELECT article_id
FROM dbo.Articles
WHERE title_hash = CAST(HASHBYTES('SHA2_256', N'Some title') AS BINARY(32))
  AND title = N'Some title';

ALTER TABLE dbo.Articles
    ADD title_prefix AS CAST(LEFT(title, 400) AS NVARCHAR(400));
CREATE INDEX IX_Articles_title_prefix ON dbo.Articles (title_prefix);

Examples

CREATE INDEX on an nvarchar(max) column

SET NOCOUNT ON;
CREATE TABLE dbo.Articles (article_id INT PRIMARY KEY, title NVARCHAR(MAX), body NVARCHAR(MAX));

CREATE INDEX IX_Articles_title ON dbo.Articles (title);

Msg 1919, Level 16, State 1, Line 4
Column 'title' in table 'dbo.Articles' is of a type that is invalid for use as a key column in an index.

PRIMARY KEY on a varchar(max) column

SET NOCOUNT ON;
CREATE TABLE dbo.Customers (
    email VARCHAR(MAX) NOT NULL PRIMARY KEY,
    name  VARCHAR(100)
);

Msg 1919, Level 16, State 1, Line 2
Column 'email' in table 'Customers' is of a type that is invalid for use as a key column in an index.
Msg 1750, Level 16, State 1, Line 2
Could not create constraint or index. See previous errors.

UNIQUE constraint on a varbinary(max) column

SET NOCOUNT ON;
CREATE TABLE dbo.Documents (doc_id INT PRIMARY KEY, file_hash VARBINARY(MAX));

ALTER TABLE dbo.Documents ADD CONSTRAINT UQ_Documents_file_hash UNIQUE (file_hash);

Msg 1919, Level 16, State 1, Line 4
Column 'file_hash' in table 'Documents' is of a type that is invalid for use as a key column in an index.
Msg 1750, Level 16, State 1, Line 4
Could not create constraint or index. See previous errors.

How to prevent it

Choose column lengths deliberately when you design a table: use (max) only for values that really can be very long, and give columns you will search, join or constrain a fixed maximum length. Check what your ORM generates, since many default strings to nvarchar(max).

Store fixed-size values such as hashes in fixed types (binary(32) for SHA-256), and replace legacy text, ntext and image columns with varchar(max), nvarchar(max) and varbinary(max). See SQL data types explained.

Common questions

Learn more on CodeWithSQL

• SQL indexes
• SQL data types explained

Official documentation

• CREATE INDEX (Transact-SQL)
• Create indexes with included columns
• Indexes on computed columns
• Database engine events and errors 1000 to 1999

Last technically reviewed 24 October 2026; examples and diagnostics run on SQL Server 2025 (17.0.1145.4). Message text checked against the engine's sys.messages catalogue.