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Hash join: Difference between revisions
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</lang>
=={{header|M2000 Interpreter}}==
<lang M2000 Interpreter>
Module HashJoin {
\\ normally we define variables when we put values to names
\\ so we can remove these two lines
Def Name$, Nemesis$
Def Long m, mc, items_size, A
\\ Lets make a container which use keys with hash function
Inventory A
\\ A now is a pointer to an Inventory, with Len(A)=0
\\ Print Type$(A)="Inventory"
\\ empty stack. We use current stack to place data
Flush
\Input B
data "Jonah", "Whales"
data "Jonah", "Spiders"
data "Alan", "Ghosts"
data "Alan", "Zombies"
data "Glory", "Buffy"
\\ Keys are unique, This is the HASH PHASE
While not empty {
Read Name$, Nemesis$
If Exist(A, Name$) Then {
m=Eval(A) ' get a pointer to array
Stack m {Data Nemesis$}
} Else Append A, Name$:=Stack:=Nemesis$ ' a stack object with one item
}
\\ Input A, this is the Long Table
data 27, "Jonah"
data 18, "Alan"
data 28, "Glory"
data 18, "Popeye"
data 28, "Alan"
\\ This is the JOIN PHASE
items_size=stack.size/2
\\ using items_size we can append data (using data) to stack
\\ $(0) is the default handler for columns.
\\ Letters justify to left, numbers to right.
\\ Letters can use more columns, and maybe wrap to more lines.
Print $(0), "Output during join"
Print "A.Age", "A.Name","B.Character", "B.Nemesis"
While items_size>0 {
Read Age, Name$
If exist(A, Name$) Then {
m=Eval(A) ' extract a pointer, this is for a stack object
mc=Each(m) ' make an iterator
While mc {
\\ we use $(1) for left justify numbers too
\\ normal StackItem$(stackobject) return top only
\\ we have to use StackItem$(stackobject, 3) to get 3rd
\\ or StackItem(stackobject, 3) if it is numeric.
\\ but here mc is iterator, and place the cursor value to it
Print $(1), Age, Name$,Name$, StackItem$(mc)
\\ so now we place at the end of current stack the same output
Data Age, Name$,Name$, StackItem$(mc)
}
}
items_size--
}
Print $(0), "Output after join"
Print "A.Age", "A.Name","B.Character", "B.Nemesis"
While not Empty {
Print $(1), Number, Letter$, Letter$, Letter$
}
Print $(0), "Output after join using format$()"
Print Format$("{0:5} {1:10} {2:10} {3:20}","A.Age", "A.Name","B.Character", "B.Nemesis")
While not Empty {
Print format$("{0::5} {1:10} {2:10} {3:20}", Number, Letter$, Letter$, Letter$)
}
}
HashJoin
</lang>
{{out}}
<pre >
27 Jonah Jonah Whales
27 Jonah Jonah Spiders
18 Alan Alan Ghosts
18 Alan Alan Zombies
28 Glory Glory Buffy
28 Alan Alan Ghosts
28 Alan Alan Zombies
</pre >
=={{header|Mathematica}} / {{header|Wolfram Language}}==
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