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Task/Hash-join/00DESCRIPTION

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+The classic [[wp:Hash Join|hash join]] algorithm for an inner join of two relations has the following steps:
+<ul>
+<li>Hash phase: Create a hash table for one of the two relations by applying a hash
+   function to the join attribute of each row. Ideally we should create a hash table for the
+   smaller relation, thus optimizing for creation time and memory size of the hash table.</li>
+<li>Join phase: Scan the larger relation and find the relevant rows by looking in the
+   hash table created before.</li>
+</ul>
+
+The algorithm is as follows:
+
+ '''for each''' tuple ''s'' '''in''' ''S'' '''do'''
+    '''let''' ''h'' = hash on join attributes ''s''(b)
+    '''place''' ''s'' '''in''' hash table ''S<sub>h</sub>'' '''in''' bucket '''keyed by''' hash value ''h''
+ '''for each''' tuple ''r'' '''in''' ''R'' '''do'''
+    '''let''' ''h'' = hash on join attributes ''r''(a)
+    '''if''' ''h'' indicates a nonempty bucket (''B'') of hash table ''S<sub>h</sub>''
+       '''if''' ''h'' matches any ''s'' in ''B''
+          '''concatenate''' ''r'' and ''s''
+       '''place''' relation in ''Q''
+
+'''Task:''' implement the Hash Join algorithm and show the result of joining two tables with it.
+You should use your implementation to show the joining of these tables:
+<table><tr><td><table border>
+  <tr><th>Age</th><th>Name</th></tr>
+  <tr><td>27</td><td>Jonah</td></tr>
+  <tr><td>18</td><td>Alan</td></tr>
+  <tr><td>28</td><td>Glory</td></tr>
+  <tr><td>18</td><td>Popeye</td></tr>
+  <tr><td>28</td><td>Alan</td></tr>
+</table></td><td><table border>
+  <tr><th>Name</th><th>Nemesis</th></tr>
+  <tr><td>Jonah</td><td>Whales</td></tr>
+  <tr><td>Jonah</td><td>Spiders</td></tr>
+  <tr><td>Alan</td><td>Ghosts</td></tr>
+  <tr><td>Alan</td><td>Zombies</td></tr>
+  <tr><td>Glory</td><td>Buffy</td></tr>
+</table></td></tr></table>