Column ‘%.*ls.%.*ls’ is not the same data type as referencing column ‘%.*ls.%.*ls’ in foreign key ‘%.*ls’.

Error Message:
Msg 1778, Level 16, State 0, Line 1
Column ‘%.*ls.%.*ls’ is not the same data type as referencing column ‘%.*ls.%.*ls’ in foreign key ‘%.*ls’.

Severity level:
16.

Description:
This error message appears when you try to create a FOREIGN KEY constraint between columns of different data types.

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

Resolution:
Error of the Severity Level 16 are generated by the user and can be fixed by the SQL Server user. The statement cannot be executed this way. FOREIGN KEY constraints should be created on columns of the same data type.

Versions:
All versions of SQL Server.

Example(s):
USE tempdb;
GO
IF OBJECT_ID(‘tempdb..t1’) > 0
 DROP TABLE t1
GO
IF OBJECT_ID(‘tempdb..t’) > 0
 DROP TABLE t
GO
CREATE TABLE t
(
 c1 CHAR(5) PRIMARY KEY
)
GO
CREATE TABLE t1
(
 c1 XML
 CONSTRAINT FK_t_t1_c1 FOREIGN KEY REFERENCES t(c1)
 ON UPDATE CASCADE
)

Remarks:
In the above example we try to create a referential integrity relation between a column of type CHAR and another column of type XML. This raises the error.




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