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The following table shows symbols of the relationship multiplicity.
| Name | Value | Notation |
|---|---|---|
| Zero | Zero |
| |
| Vertical | One |
| |
Crow's foot | Many |
|
Multiplicity lower bounds and upper bounds are paired into one adornment, as shown in the following table. Note that any lower bound, which is more that 0 is treated as 1 (this also includes lower bounds greater than 1, such as 2.). Also, any upper bound which is greater than 1 is treated as Many (this also includes upper bounds less than unlimited, such as 7.).
| Min | Max | Read as | Figure |
|---|---|---|---|
| 0 | 1 | One (optional) |
| ||
| 1 | 1 | One (mandatory) |
| ||
| 0 | Many | Many (optional) |
| ||
| 1 | Many | Many (mandatory) |
|
Basic ER diagram example.
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