Tikz how to draw a line to rectangle split

Question

I am drawing an ER-diagram and would like to show the relationships between tables.

I managed to create the tables:

\documentclass{article}
\usepackage[cm]{fullpage}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes,positioning}

\tikzset{
  outernode/.style={draw,ultra thick,inner sep=0},
  innernode/.style={inner sep=.3333em,draw,rectangle split}
}
\newcommand\innernode[2]{\tikz\node[innernode,rectangle split parts=#1]{#2};}

\begin{document}
\begin{tikzpicture}
  \node (1) [outernode]
       { \innernode 2 {sco\_groups \nodepart{second} id} } ;
  \node (2) [below= 1cm of 1.south east, anchor=north west, outernode]
       { \innernode 3 {sco\_index \nodepart{second} tid \nodepart{third} sco\_id} } ;
\end{tikzpicture}
\end{document}

But don't know, how to create the line, uniting them (I marked it with red).

Answer 1

Update:

I don't think using a \tikz \node (earlier solution -- below) is what you should be using. At least I could not figure out how to get access to particular nodepart with that method. So there are three updates here:

• As per Jake's suggestions, it is easier to just simply use (1.south) |- (2.two west) to draw the line shown in red. Now to make a connection to the sco_id you can just access the side of this node via (2.three west).
• The \innernode TeX macro has been eliminated.
• The innernode style has been enhanced to accept an additional parameter to allow you to specify the number of inner nodes.

So, now you can easily access any nodepart you desire:

---

You can connect them via (1.south) -- ($(1.south |- 2.west)$) -- (2.west):

---

Code: Updated

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes, positioning}

\tikzset{
  outernode/.style={draw,ultra thick, inner sep=0},
  innernode/.style={inner sep=.3333em, draw, rectangle split, rectangle split parts=#1}
}

\begin{document}
\begin{tikzpicture}
    \node [outernode] (1)
        [innernode=2] { sco\_groups \nodepart{second} id} ;

    \node[below=1cm of 1.south east, anchor=north west, outernode] (2) 
        [innernode=3] {
            sco\_index 
            \nodepart{second} tid
            \nodepart{third} sco\_id
    };

    \draw [blue, ultra thick]  (1.-40)   |- (2.one west);
    \draw [red,  ultra thick]  
            (1.south)    node [below left, black] {$1$} |- 
            (2.two west) node [above left, black] {$n$};
    \draw [olive,   ultra thick]  (1.-140)   |- (2.three west);
\end{tikzpicture}
\end{document}

---

Code: Original

\documentclass{article}
\usepackage[cm]{fullpage}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes,positioning}
\usetikzlibrary{calc}

\tikzset{
  outernode/.style={draw,ultra thick,inner sep=0},
  innernode/.style={inner sep=.3333em,draw,rectangle split}
}
\newcommand\innernode[2]{\tikz\node[innernode,rectangle split parts=#1]{#2};}

\begin{document}
\begin{tikzpicture}
  \node (1) [outernode]
       { \innernode 2 {sco\_groups \nodepart{second} id} } ;
  \node (2) [below= 1cm of 1.south east, anchor=north west, outernode]
       { \innernode 3 {sco\_index \nodepart{second} tid \nodepart{third} sco\_id} } ;

\draw [red, ultra thick] 
        (1.south) node [below left, black] {$1$} -- 
        ($(1.south |- 2.west)$) -- 
        (2.west) node [above left, black] {$n$};
\end{tikzpicture}
\end{document}