func NewLiteral(value interface{}, fieldType sql.Type) *Literal {
	return &Literal{
		value:     value,
		fieldType: fieldType,
	}
}
NewLiteral creates a new Literal expression.
package expression
import (
	"fmt"
	"github.com/src-d/go-mysql-server/sql"
)
type Literal struct {
	value     interface{}
	fieldType sql.Type
}