increment column value with an integer when it is a duplicate

Question

I have a layer with around 1000 lines. Some Name are repeated several times and I wish to have every name unique. Thus I try in the field calculator to add an integer at the end of the name only when it is a duplicate, and of course I want to increment the integer value each time it is used. As an example, in my layer I have in the Column 'Name':

Name_One
Name_One
Name_Two
Name_Two
Name_One

And I would like it to become

Name_One1
Name_One2
Name_Two1
Name_Two2
Name_One3

I tried first to identify the duplicate with the function

if(count("Name", "Name") = 1, 1, 0)

Then with the new column "uniqueness" that hold the value of the previous command I try

CASE
    WHEN 'uniqueness' = 0 THEN @a
    WHEN 'uniqueness' = 0 THEN @a = @a+1
    ELSE @a = 1
END

(@a is a project variable equal to 1)

But it doesn't work.

How can I do that?

Answer 1

QGIS 3.0/3.2

(1) Use Add autoincremental field tool (in Processing Toolbox | Vector table) to create new incremental number field.

• Input layer: your layer
• Field name: any name (default value is AUTO)
• Start values at: 1
• Group values by: select your column Name
• Advanced parameters - Sort expression: select id

(2) Put Name and AUTO fields together

Open the Field Calculator and create a new field by concat("Name", "AUTO")