If someone wants to read post $post_id in language $language_name,

my $sth = $dbh->prepare('
   SELECT *
     FROM post_translations
     JOIN posts
       ON post_translations.post_translation_id = posts.post_translati
+on_id
     JOIN languages
       ON post_translations.lang_id = languages.lang_id
    WHERE posts.post_id = ?
      AND languages.lang_name = ?
');

$sth->execute($post_id, $language_name);
[download]

Pardon any syntax errors.

How would I use the `post` table with an auto_increment field `post_id` and only 1 field `post_translation_id` to have more than one translation per post?

You woulnd't. You'd fix my bug :)

If you wanted to have it autoincrement,

CREATE TABLE `languages` (
    `lang_id` TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    `lang_name` VARCHAR(60) NOT NULL
);

CREATE TABLE `post_translations` (
    `post_translation_id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRI
+MARY KEY,
    `post_translation_cat` INT(11) UNSIGNED NOT NULL,
    `post_translation_date` DATETIME NOT NULL,
    `post_translation_title` VARCHAR(255) NOT NULL,
    `post_translation_body` TEXT NOT NULL,
    `post_translation_lang` TINYINT UNSIGNED NOT NULL
);

CREATE TABLE `posts` (
    `post_id`, INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
);

CREATE TABLE `post_to_translation` (
    `post_id`, INT(11) UNSIGNED NOT NULL,
    `post_translation_id` INT(11) UNSIGNED NOT NULL,
);
[download]

Update: Since it's an 1:N and not N:N relationship, post_to_translation is not necessary.

CREATE TABLE `languages` (
    `lang_id` TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    `lang_name` VARCHAR(60) NOT NULL
);

CREATE TABLE `post_translations` (
    `post_id`, INT(11) UNSIGNED NOT NULL,
    `post_translation_id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRI
+MARY KEY,
    `post_translation_cat` INT(11) UNSIGNED NOT NULL,
    `post_translation_date` DATETIME NOT NULL,
    `post_translation_title` VARCHAR(255) NOT NULL,
    `post_translation_body` TEXT NOT NULL,
    `post_translation_lang` TINYINT UNSIGNED NOT NULL
);

CREATE TABLE `posts` (
    `post_id`, INT(11) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
);
[download]