I was looking at the notation from the textbook I'm using to learn relational algebra and other DBMS related information, and I noticed that I don't know how to typeset the symbol shown below.
I know there is a command in the amssymb package and related packages to produce the standard unicode symbols for outerjoins. Is there a package somewhere using this symbol?
You might use \overset{\circ}{\bowtie} to get
However, this doesn't really resemble the symbol you show. You can try
\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\makeatletter
\newcommand{\circleouterjoin}{\mathrel{\mathpalette\circleouterjoin@\relax}}
\newcommand{\circleouterjoin@}[2]{%
\ooalign{%
\hidewidth\raisebox{1.1\height}{\scalebox{0.9}{$\m@th#1\circ$}}\hidewidth\cr
$\m@th#1\bowtie$\cr
}%
}
\makeatother
\begin{document}
The \emph{outerjoin} $R\circleouterjoin S$
In subscripts $X_{R\circleouterjoin S}$
\end{document}
You may play with 0.9 (scaling factor) and 1.1 (raising factor) until you're fully satisfied.
You might not be happy with \bowtie that has “interlacing”.
\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\makeatletter
\newcommand{\outerjoin}{%
\mathrel\triangleright
\mathrel{\mkern-2mu}%
\mathrel\triangleleft
}
\newcommand{\circleouterjoin}{\mathrel{\mathpalette\circleouterjoin@\relax}}
\newcommand{\circleouterjoin@}[2]{%
\ooalign{%
\hidewidth\raisebox{1.1\height}{\scalebox{0.9}{$\m@th#1\circ$}}\hidewidth\cr
$\m@th#1\outerjoin$\cr
}%
}
\makeatother
\begin{document}
The \emph{outerjoin} $R\circleouterjoin S$
In subscripts $X_{R\circleouterjoin S}$
\end{document}
Explanation: in \bowtie the backing up is 3mu.
With :
\documentclass[11pt]{article}
\usepackage{mathtools}
\newcommand{\outerjoin}{\overset{\circ}{\bowtie}}
\begin{document}
The \emph{outerjoin} $R \outerjoin S$.
\end{document}
you obtain:
\circabove the join symbol using\stackrel(inamsmath).