Why do I get “Procedure expects parameter '@statement' of type 'ntext/nchar/nvarchar'.” when I try to use sp_executesql?

Question

Why do I get this error

Procedure expects parameter '@statement' of type 'ntext/nchar/nvarchar'.

when I try to use sp_executesql?

Answer 1

Sounds like you're calling sp_executesql with a VARCHAR statement, when it needs to be NVARCHAR.

e.g. This will give the error because @SQL needs to be NVARCHAR

DECLARE @SQL VARCHAR(100)
SET @SQL = 'SELECT TOP 1 * FROM sys.tables'
EXECUTE sp_executesql @SQL

So:

DECLARE @SQL NVARCHAR(100)
SET @SQL = 'SELECT TOP 1 * FROM sys.tables'
EXECUTE sp_executesql @SQL

Answer 2

The solution is to put an N in front of both he type and the SQL string to indicate it is a double-byte character string:

DECLARE @SQL NVARCHAR(100) 
SET @SQL = N'SELECT TOP 1 * FROM sys.tables' 
EXECUTE sp_executesql @SQL