code: func SqlFunc(funcName string, expressions ...Expression) Expression {
  	f := &funcExpression{
  		funcName: funcName,
  	}
  	if len(expressions) > 0 {
  		args := make([]Clause, len(expressions), len(expressions))
  		for i, expr := range expressions {
  			args[i] = expr
  		}
  
  		f.args = &listClause{
  			clauses:            args,
  			includeParentheses: true,
  		}
  	}
  	return f
  }
docs: // Returns a representation of sql function call "func_call(c[0], ..., c[n-1])