Cannot create two constraints named '%.*ls'. Duplicate constraint names are not allowed.

Error Message:
Msg 8168, Level 16, State 0, Line 1
Cannot create two constraints named '%.*ls'. Duplicate constraint names are not allowed.

Severity level:
16.

Description:
This error message appears when you try to create a table and use a constraint name more than once.

Consequences:
The T-SQL statement can be parsed, but causes the error at runtime.

Resolution:
Errors of the Severity Level 16 are generated by the user and are corrigible by the user. The statement cannot be executed this way. Constraint names must be unique.

Versions:
All versions of SQL Server.

Example(s):
USE tempdb;
IF OBJECT_ID('tempdb.#t') > 0
 DROP TABLE #t
GO
CREATE TABLE #t
(
 c1 INT
 CONSTRAINT chk_1 CHECK(c1<10),
 c2 INT
 CONSTRAINT chk_1 CHECK(c2>c1)
)
GO

Remarks:
In the above example we try to create the table #t with two constraints named chk_1. This raises the error.