mysql - Proper way to create composite PK -

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as far know, there 2 ways of creating composite pk, dont know differences or one:

create table appusers ( id int not null, username varchar(20) not null, lastname varchar(100), firstname varchar(100), primary key (id, username) )

vs

create table appusers ( id int not null, username varchar(20) not null, lastname varchar(100), firstname varchar(100), constraint pk_appusers primary key (id, username) )

specifications:

according http://dev.mysql.com/doc/refman/5.0/en/create-table.html , http://dev.mysql.com/doc/refman/5.0/en/alter-table.html, constraint key word optional primary key.

best practice:

i say, use 1 whichever prefer regarding readability. i'd tend limit letters though, using join instead of inner join.


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