slight adjustment

Signed-off-by: Andrew Thornton <art27@cantab.net>

internal/statements/upsert.go

@@ -175,7 +175,7 @@ func (statement *Statement) genMergeSQL(doUpdate bool, columns []string, args []
 	}
 	write(" WHEN NOT MATCHED THEN INSERT ")
 	includeAutoIncrement := statement.includeAutoIncrement(columns)
-	if len(columns) == 0 {
+	if len(columns) == 0 && statement.dialect.URI().DBType == schemas.MSSQL {
 		write(" DEFAULT VALUES ")
 	} else {
 		// We have some values - Write the column names we need to insert: