Group by element and sum values XSLT - sum

Question

I am new to XSLT and I am stuck on a problem. I've done some searches I read about Muenchian grouping but I do not know how to use it in this prorblem.
I am trying to write code in XSLT to read every teamName and sum the goals of each teams.
I am using XML v 1.0
Below is my current data file in XML:
<footballLeague>
<round num="1">
<match>
<local>
<teamName>AA</teamName>
<goals>0</goals>
</local>
<visitor>
<teamName>BB</teamName>
<goals>1</goals>
</visitor>
</match>
<match>
<local>
<teamName>CC</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>DD</teamName>
<goals>0</goals>
</visitor>
</match>
</round>
<round num="2">
<match>
<local>
<teamName>DD</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>AA</teamName>
<goals>1</goals>
</visitor>
</match>
<match>
<local>
<teamName>BB</teamName>
<goals>0</goals>
</local>
<visitor>
<teamName>CC</teamName>
<goals>1</goals>
</visitor>
</match>
</round>
<round num="3">
<match>
<local>
<teamName>DD</teamName>
<goals>0</goals>
</local>
<visitor>
<teamName>BB</teamName>
<goals>1</goals>
</visitor>
</match>
<match>
<local>
<teamName>CC</teamName>
<goals>0</goals>
</local>
<visitor>
<teamName>AA</teamName>
<goals>1</goals>
</visitor>
</match>
</round>
<round num="4">
<match>
<local>
<teamName>BB</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>AA</teamName>
<goals>0</goals>
</visitor>
</match>
<match>
<local>
<teamName>DD</teamName>
<goals>0</goals>
</local>
<visitor>
<teamName>CC</teamName>
<goals>1</goals>
</visitor>
</match>
</round>
<round num="5">
<match>
<local>
<teamName>AA</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>DD</teamName>
<goals>1</goals>
</visitor>
</match>
<match>
<local>
<teamName>CC</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>BB</teamName>
<goals>1</goals>
</visitor>
</match>
</round>
<round num="6">
<match>
<local>
<teamName>BB</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>DD</teamName>
<goals>0</goals>
</visitor>
</match>
<match>
<local>
<teamName>AA</teamName>
<goals>1</goals>
</local>
<visitor>
<teamName>CC</teamName>
<goals>0</goals>
</visitor>
</match>
</round>
</footballLeague>
The output I would like to achieve after running the XSLT is:
Team Name | Goals For | Goals against | Games Won | Tied Matches
AA | 4 | 4 | 2 | 2
BB | 5 | 2 | 4 | 1
CC | 4 | 3 | 3 | 1
DD | 2 | 6 | 0 | 2
Any help to get me started would be fantastic!

Answer 1

See if this can get you started:
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="score" match="local|visitor" use="teamName" />
<xsl:template match="footballLeague">
<stats>
<xsl:for-each select="round/match/*[count(. | key('score', teamName)[1]) = 1]">
<team>
<xsl:copy-of select="teamName"/>
<goals-for>
<xsl:value-of select="sum(key('score', teamName)/goals)"/>
</goals-for>
<goals-against>
<xsl:value-of select="sum(key('score', teamName)[self::local]/../visitor/goals) + sum(key('score', teamName)[self::visitor]/../local/goals)"/>
</goals-against>
</team>
</xsl:for-each>
</stats>
</xsl:template>
</xsl:stylesheet>
Applied to your example, the result will be:
<?xml version="1.0" encoding="UTF-8"?>
<stats>
<team>
<teamName>AA</teamName>
<goals-for>4</goals-for>
<goals-against>4</goals-against>
</team>
<team>
<teamName>BB</teamName>
<goals-for>5</goals-for>
<goals-against>2</goals-against>
</team>
<team>
<teamName>CC</teamName>
<goals-for>4</goals-for>
<goals-against>3</goals-against>
</team>
<team>
<teamName>DD</teamName>
<goals-for>2</goals-for>
<goals-against>6</goals-against>
</team>
</stats>