One to One Relationship in Salesforce

We all know about the 1-M && M-M relationship(using junction Object) in salesforce.
Some times we may need 1-1 relationship among two objects.
but Unfortunately Salesforce doesnot allow any direct methodolgy to build 1-1 relationship

We can achieve the same by workflow or trigger. But workflow is more flexible & the easier way

Steps
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Say Two Objects OBJECT-A and OBJECT-B

1- create a look up field in one object
    say in OBJECT-A, there is a lookup to OBJECT-B
    field Name= obj-B (say)

2- Create another textfield at same Object with unique property (used to hold same obj-B field value)
     fieldName= unique_Obj-B (say)

3- Define a workFlow Rule /Trigger to  Update the custom "unique_Obj-B" field with the value of the associated OBJECT-B ID.(i.e the field value of "obj-B")

Now we have done with 1-1 Relationship
When we try to add a second same OBJECT-B to the OBJECT-A, the "unique" constraint in OBJECT-A (field "unique_Obj-B")would be violated and an error would be thrown.....