The MySQL UNIQUE
constraint is often used in a
column definition in which we need each value for that column to
be distinct from the others. Perhaps it is an email column for an
on-line registration form and we want to ensure that users cannot
register twice for an account using the same email. Whatever the
case may be, UNIQUE
is there to help us ensure this
type of data integrity or business requirement. What if the
target table already exists and you determine you need to add a
UNIQUE
constraint to an existing column? In this
post, I will cover 2 ways you can implement a UNIQUE
constraint on existing columns using the phpMyAdmin web
interface…
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