如何在列表中获得正确的垂直对齐

Question

我正在用 LaTeX 写一些 SQL 代码，但渲染效果不太令人满意。我会留下我写的代码

\begin{lstlisting}
create table Dipartimento
(
    Codice          char(3) primary key,
    Nome            varchar(50)
);

create table Impiegato
(
    Matricola       char(4) primary key,
    Nome            varchar(30),
    Cognome         varchar(30),
    CodDip          char(3) 
                    references Dipartimento (Codice)
                    on update cascade
                    on delete set null
)
\end{lstlisting}

呈现为：

我实际使用的列出包的选项如下

\lstset{frame=false, %trblr, false, none
language=SQL,
aboveskip=3mm,
belowskip=3mm,
showstringspaces=false,
columns=flexible,
basicstyle=\ttfamily,
numbers=left, %=left (numera le righe di codice)
numberstyle=\color{gray}, %\tiny per diminuire dimensione
keywordstyle=\bfseries,
%commentstyle=\color{dkgreen},
%stringstyle=\color{mauve},
breaklines=true,
breakatwhitespace=true,
tabsize=4,
captionpos=b,
backgroundcolor=\color{black!10},
morekeywords={references},
showstringspaces=false,
tab=$\bullet$\space,
showtabs=true,
%stringstyle=\rmfamily,
% vocali accentate
inputencoding=utf8, 
extendedchars=true,
literate={à}{{\`a}}1 {°}{{\textdegree}}1
}

如下图所示（我设置了 showtabs=true 选项），垂直对齐有点不对，导致单词不对齐。我该如何解决这个问题？提前致谢

编辑：测试代码

\documentclass{article}
\usepackage{xcolor}
\usepackage{listings}
\lstset{frame=false, %trblr, false, none
language=SQL,
aboveskip=3mm,
belowskip=3mm,
showstringspaces=false,
columns=flexible,
basicstyle=\ttfamily,
numbers=left, %=left (numera le righe di codice)
numberstyle=\color{gray}, %\tiny per diminuire dimensione
keywordstyle=\bfseries,
%commentstyle=\color{dkgreen},
%stringstyle=\color{mauve},
breaklines=true,
breakatwhitespace=true,
tabsize=4,
captionpos=b,
backgroundcolor=\color{black!10},
morekeywords={references},
showstringspaces=false,
tab=$\bullet$\space,
showtabs=true,
%stringstyle=\rmfamily,
% vocali accentate
inputencoding=utf8, 
extendedchars=true,
literate={à}{{\`a}}1 {°}{{\textdegree}}1
}

\begin{document}
\begin{lstlisting}
create table Dipartimento
(
Codice          char(3) primary key,
Nome            varchar(50)
);

create table Impiegato
(
Matricola        char(4) primary key,
Nome             varchar(30),
Cognome          varchar(30),
CodDip           char(3) 
                 references Dipartimento (Codice)
                 on update cascade
                 on delete set null
)
\end{lstlisting}
\end{document}

在空白文档中，使用相同的选项，我得到了我想要的结果...发生了什么？