sql - Making a column having an "unique" value depending on the value of another column -

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let's have simple table called "characters":

realm_id | character_name | xp ---------|----------------|----------        1 |     "mike"     | 10        1 |     "lara"     | 25        2 |     "mike"     | 40

what want have unique names depending on realm_id. so, example, while having 2 "mikes" different realm_ids allowed, it's not allowed have 2 "mikes" within same realm_id. possible?

if you're looking perform select statement on data you'll looking (assuming highest xp wins);

select realm_id character_name max(xp) xp characters

however, if want table not allow duplicates in first place you're best looking @ making teh realm_id , character_name composite primary key. stop duplication happening in first place although you'll have consider happens when tries insert duplicate, it'll throw error.


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