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.. (לתיקייה המכילה) | |
In question 3, can a student be a friend of himself in the Friends table? | |
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No |
In question 4, should we enforce that the Friends table cannot have a student that is a friend of himself? | |
| You don't must but you can. |
In question 4 , when creating the Friends table, should we enforce that if tuple (id1,id2) exists, tuple (id2,id1) also exists? | |
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No need to enforce it when creating the table, and also when inserting to the table. It is OK if you already have inserted symmetrically, you can insert 3 tuple instead of 2 . Any case, the last one should be the "problematic" one in other terms than symmetry. |
In question 3, if the tuple (id1,id2) appears in the Friends table, does it mean that the tuple (id2,id1) also appears ? | |
| Yes |