ERD LateX doodles

demo_arrowlines.tex

\draw [one to one] (0,0) -- (12,0)  node[midway, above] {can't work out the layout} ;

\draw [one to one] (0,2) -- (5,2) node[midway, above] {one to one} ;
\draw [many to many] (7,2) -- (12,2) node[midway, above] {many to many} ;

\draw [many to one] (0,4) -- (5,4) node[midway, above] {many to one} ;
\draw [one to many] (7,4) -- (12,4)  node[midway, above] {one to many} ;

\draw [many to oone] (0,6) -- (5,6) node[midway, above] {many to oone} ;
\draw [oone to many] (7,6) -- (12,6)  node[midway, above] {oone to many} ;

\draw [many to omany] (0,8) -- (5,8) node[midway, above] {many to omany} ;
\draw [omany to many] (7,8) -- (12,8)  node[midway, above] {omany to many} ;


\draw [omany to none] (0,10) -- (5,10) node[midway, above] {omany to none} ;
\draw [none to omany] (7,10) -- (12,10) node[midway, above] {none to omany} ;


\draw [omany to one] (0,12) -- (5,12) node[midway, above] {omany to one} ;
\draw [one to omany] (7,12) -- (12,12) node[midway, above] {one to omany} ;

\draw [omany to oone] (0,14) -- (5,14) node[midway, above] {omany to oone} ;
\draw [oone to omany] (7,14) -- (12,14) node[midway, above] {oone to omany} ;


\draw [one to none] (0,16) -- (5,16) node[midway, above] {one to none} ;
\draw [none to one] (7,16) -- (12,16) node[midway, above] {none to one} ;

\draw [oone to one] (0,18) -- (5,18) node[midway, above] {oone to one} ;
\draw [one to oone] (7,18) -- (12,18) node[midway, above] {one to oone} ;


\draw [oone to none] (0,20) -- (5,20) node[midway, above] {oone to none} ;
\draw [none to oone] (7,20) -- (12,20) node[midway, above] {none to oone} ;

erd.py

latex='''
%via https://www.reddit.com/r/LaTeX/comments/2pwu0g/made_a_diagram_in_tikz_not_sure_how_to_improve/
%via https://tex.stackexchange.com/questions/393560/tikz-crows-foot-notation-on-only-one-side-for-documentation

\documentclass{{standalone}} 
\usepackage{{tikz}}
\usetikzlibrary{{shapes.multipart}}
\usetikzlibrary{{matrix}}
\usetikzlibrary{{positioning}}
\usetikzlibrary{{shadows}}
\usetikzlibrary{{calc}}

\usetikzlibrary{{%
    chains,
}}
\tikzset{{
    entity/.code={{
        \tikzset{{
            %label=above:#1,
            name=#1,
            inner sep=0pt,
            every entity/.try,
            fill=white,
            %general shadow={{
            %    shadow xshift=0.0625in,
            %    shadow yshift=-0.0625in,
            %    opacity=0.2,
            %    fill=black!50
            %}}
        }}%
        \def\entityname{{#1}}%
    }},
     entity anchor/.style={{matrix anchor=#1.center}},
    every entity/.style={{
            draw,
    }},
    every property/.style={{
        % inner xsep=0.25cm (the align center is for just the single box' define a new element for that?
        align=center, inner ysep=0.525cm, anchor=west, text width=1.5in
    }},
    dummy/.style={{
        rectangle,
        rounded corners,
        draw=white, very thick,
        text centered}},
    zig zag to/.style={{
        to path={{(\tikztostart) -| ($(\tikztostart)!#1!(\tikztotarget)$) |- (\tikztotarget) \tikztonodes}}
    }},
    zig zag to/.default=0.5,
    one to one/.style={{
        one-one, zig zag to
    }},    
    one to none/.style={{
        one-, zig zag to
    }},    
    none to one/.style={{
        -one, zig zag to
    }},
    none to oone/.style={{
        -oone, zig zag to
    }},
    oone to one/.style={{
        oone-one, zig zag to
    }},
    one to oone/.style={{
        one-oone, zig zag to
    }},
    none to omany/.style={{
        -omany, zig zag to
    }},
    oone to none/.style={{
        oone-, zig zag to
    }},    
    omany to none/.style={{
        omany-, zig zag to
    }}, 
    omany to one/.style={{
        omany-one, zig zag to
    }},
    one to omany/.style={{
        one-omany, zig zag to
    }},
    one to many/.style={{
        one-crow's foot, zig zag to,
    }}, 
    many to one/.style={{
        crow's foot-one, zig zag to
    }},
    oone to many/.style={{
        oone-crow's foot, zig zag to,
    }}, 
    many to oone/.style={{
        crow's foot-oone, zig zag to
    }},
    many to omany/.style={{
        crow's foot-omany, zig zag to
    }}, 
    omany to many/.style={{
        omany-crow's foot, zig zag to
    }}, 
    many to many/.style={{
        crow's foot-crow's foot, zig zag to
    }}, 
    oone to omany/.style={{
        oone-crow's foot, zig zag to
    }}, 
    omany to oone/.style={{
        crow's foot-oone, zig zag to
    }}, 
}}    
\makeatletter
\pgfarrowsdeclare{{crow's foot}}{{crow's foot}}
{{
    \pgfarrowsleftextend{{+-.5\pgflinewidth}}%
    \pgfarrowsrightextend{{+.5\pgflinewidth}}%
}}
{{
    \pgfutil@tempdima=0.6pt%
    %\advance\pgfutil@tempdima by.25\pgflinewidth%
    \pgfsetdash{{}}{{+0pt}}%
    \pgfsetmiterjoin%
    \pgfpathmoveto{{\pgfqpoint{{0pt}}{{-9\pgfutil@tempdima}}}}%
    \pgfpathlineto{{\pgfqpoint{{-13\pgfutil@tempdima}}{{0pt}}}}%
    \pgfpathlineto{{\pgfqpoint{{0pt}}{{9\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{-8pt}}{{-6pt}}}}% 
    \pgfpathlineto{{\pgfqpoint{{-8pt}}{{-6pt}}}}%  
    \pgfpathlineto{{\pgfqpoint{{-8pt}}{{6pt}}}}% 
    \pgfusepathqstroke%
}}

\pgfarrowsdeclare{{omany}}{{omany}}
{{
    \pgfarrowsleftextend{{+-.5\pgflinewidth}}%
    \pgfarrowsrightextend{{+.5\pgflinewidth}}%
}}
{{
    \pgfutil@tempdima=0.6pt%
    %\advance\pgfutil@tempdima by.25\pgflinewidth%
    \pgfsetdash{{}}{{+0pt}}%
    \pgfsetmiterjoin%
    \pgfpathmoveto{{\pgfqpoint{{0pt}}{{-9\pgfutil@tempdima}}}}%
    \pgfpathlineto{{\pgfqpoint{{-13\pgfutil@tempdima}}{{0pt}}}}%
    \pgfpathlineto{{\pgfqpoint{{0pt}}{{9\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%  
    \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{-6pt}}{{-6pt}}}}% 
    \pgfpathcircle{{\pgfpoint{{-11.5pt}}{{0}}}} {{3.5pt}}
    \pgfusepathqstroke%
}}

\pgfarrowsdeclare{{oone}}{{oone}}
{{
    \pgfarrowsleftextend{{+-.5\pgflinewidth}}%
    \pgfarrowsrightextend{{+.5\pgflinewidth}}%
}}
{{
    \pgfutil@tempdima=0.6pt%
    %\advance\pgfutil@tempdima by.25\pgflinewidth%
    \pgfsetdash{{}}{{+0pt}}%
    \pgfsetmiterjoin%
     \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{-6pt}}{{-6pt}}}}% 
    \pgfpathlineto{{\pgfqpoint{{-6pt}}{{-6pt}}}}%  
    \pgfpathlineto{{\pgfqpoint{{-6pt}}{{6pt}}}}% 
    \pgfpathcircle{{\pgfpoint{{-11.5pt}}{{0}}}} {{3.5pt}}
    \pgfusepathqstroke%
}}

\pgfarrowsdeclare{{one}}{{one}}
{{
    \pgfarrowsleftextend{{+-.5\pgflinewidth}}%
    \pgfarrowsrightextend{{+.5\pgflinewidth}}%
}}
{{
    \pgfutil@tempdima=0.6pt%
    %\advance\pgfutil@tempdima by.25\pgflinewidth%
    \pgfsetdash{{}}{{+0pt}}%
    \pgfsetmiterjoin%
    \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{-6pt}}{{-6pt}}}}% 
    \pgfpathlineto{{\pgfqpoint{{-6pt}}{{-6pt}}}}%  
    \pgfpathlineto{{\pgfqpoint{{-6pt}}{{6pt}}}}% 
    \pgfpathmoveto{{\pgfqpoint{{0\pgfutil@tempdima}}{{0\pgfutil@tempdima}}}}%
    \pgfpathmoveto{{\pgfqpoint{{-8pt}}{{-6pt}}}}% 
    \pgfpathlineto{{\pgfqpoint{{-8pt}}{{-6pt}}}}%  
    \pgfpathlineto{{\pgfqpoint{{-8pt}}{{6pt}}}}%    
    \pgfusepathqstroke%
}}

\def\property#1{{\node[name=\entityname-#1, every property/.try]{{#1}};}}
\def\properties{{\begingroup\catcode`\_=11\relax\processproperties}}
\def\processproperties#1{{\endgroup%
    \def\propertycode{{}}%
    \foreach \p in {{#1}}{{%
        \expandafter\expandafter\expandafter\gdef\expandafter\expandafter\expandafter\propertycode%
        \expandafter\expandafter\expandafter{{\expandafter\propertycode\expandafter\property\expandafter{{\p}}\\}}%
    }}%
    \propertycode%
}}

%The following is for handling foreign and primary keys
\def\pk#1{{\node[name=\entityname-#1, every property/.try]{{#1}};
    \node[name=\entityname-#1, every property/.try, red, text width=1in, align=right,]{{(PK)}};
    \\}}
\def\fk#1{{\node[name=\entityname-#1, every property/.try]{{#1}};
    \node[name=\entityname-#1, every property/.try, red, text width=1in, align=right]{{(FK)}};
    \\}}    

\begin{{document}}


\begin{{tikzpicture}}

{diag}

\end{{tikzpicture}}


\end{{document}}
'''.format(diag=diag)

example_erd.py

diag='''
\matrix [entity=Customer, entity anchor=Customer-Customer]  {
    \properties{
        Customer
    }
};

\matrix  [entity=DiskOrder, below=3cm of Customer-Customer, entity anchor=DiskOrder-DiskOrder]  {
    \properties{
        DiskOrder
    }
};

\matrix  [entity=OrderItem, below=3cm of DiskOrder-DiskOrder, entity anchor=OrderItem-OrderItem]  {
    \properties{
        OrderItem     
    }
};



\draw [one to omany] (Customer-Customer) -- (DiskOrder-DiskOrder)  ;
\draw [one to many] (DiskOrder-DiskOrder) -- (OrderItem-OrderItem) ;
'''