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| Types of Relations |
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| There are four types of relations as follows: |
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| (i) one - one |
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| (ii) many - one |
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| (iii) one - many |
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| (iv) many - many |
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| For each element of B there is one corresponding element of A |
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| For an element of B there is more than one element of A. |
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| For one element of A there is more than one corresponding element of B. |
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| For one element of A there is more than one corresponding element of B and for one element of B there is more than one corresponding element of A. |
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| The relation is called 'onto' if every element of B has a corresponding element of A. |
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| For example, Figures (i) and (ii) are onto relations. |
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| The relation is called 'into' if every element of B does not have a corresponding element of A. |
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| For example, Figures (iii) and (iv) are into relations. |
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