BOL - Transact-SQL Reference - System Stored Procedures - sp_executesql

"sp_executesql [@stmt =] stmt[{,[@params =] N'@parameter_name data_type [,...n]' }{,[@param1 =] 'value1' [,...n] }
]

Arguments
[@stmt =] stmt

Is a Unicode string containing a Transact-SQL statement or batch. stmt must be either a Unicode constant or a variable that can be implicitly converted to ntext. More complex Unicode expressions (such as concatenating two strings with the + operator) are not allowed. Character constants are not allowed. If a constant is specified, it must be prefixed with an N. For example, the Unicode constant N'sp_who' is legal, but the character constant 'sp_who' is not. The size of the string is limited only by available database server memory"

Надо так
declare @sQuery nvarchar(255)
set @sQuery = N'insert into tablse_name (column) values(value)'
exec sp_executesql @sQuery