How to add Primary key to an existing column of an already populated table

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I have a table already populated, in this table I have the column Deviceimei which I want to turn into Primary key. Is there any way to do this without having to empty the table ?

I’m trying this way:

alter table TableName add constraind PK_DeviceIMEI primary key (DeviceIMEI)
sql-server

  • Are you making a mistake? If so, what mistake?

  • would not be add constraint ??? is wrong there

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Yes you do, the command is a ALTER TABLE:

ALTER TABLE nome-da-tablea ADD PRIMARY KEY (nome-do-campo)

Now, the contents of the field must respect the rules of a Primary key (quoted from the link above):

Limitations and Restrictions A table can contain only one PRIMARY KEY Constraint.

  • All Columns defined Within a PRIMARY KEY Constraint must be defined as NOT NULL.
  • If nullability is not specified, all Columns Participating in a PRIMARY KEY Constraint have their nullability set to NOT NULL.

That is to say:

  • The table can only have a primary key
  • If not specified, fields that are part of the Primary key must be non-null

If you have duplicated values in the key will give error, so just validate/correct/delete the data that do not respect the rules of Primary key that will work

  • I edited the question by adding an example of how I am trying to make the change. If you can point out where the error is thanks.

  • I commented there, if this command is the same as the question constraint is wrong, but can use only add primary key

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