[Dovecot] tables between dovecot and postfix and a paradoxical question

[Mohsen Pahlevanzadeh]

Dear all,

I read we create the following table in wiki2 :
CREATE TABLE users (
    userid VARCHAR(128) NOT NULL,
    domain VARCHAR(128) NOT NULL,
    password VARCHAR(64) NOT NULL,
    home VARCHAR(255) NOT NULL,
    uid INTEGER NOT NULL,
    gid INTEGER NOT NULL
);

But i read the following text in the official postfix documentation :
      "DO create tables with each matching item as a key and with
       an arbitrary value. With SQL databases it is not  uncommon
       to return the key itself or a constant value."
ref: http://www.postfix.org/mysql_table.5.html

How can i combine together?

--mohsen