Php Wordpress插件表在更新到4.2后不会创建

我正在创建一个wordpress插件。这个插件创建一些自定义表。使用WordPress4.1，一切正常。更新到4.2后，插件只创建教师和假期表。这是我的密码：

register_activation_hook( __FILE__, 'utt_install' );

function utt_install(){

    require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
    global $wpdb;
    $periodsTable=$wpdb->prefix."utt_periods";
    $subjectsTable=$wpdb->prefix."utt_subjects";
    $groupsTable=$wpdb->prefix."utt_groups";
    $teachersTable=$wpdb->prefix."utt_teachers";
    $classroomsTable=$wpdb->prefix."utt_classrooms";
    $lessonsTable=$wpdb->prefix."utt_lessons";
    $holidaysTable=$wpdb->prefix."utt_holidays";
    $eventsTable=$wpdb->prefix."utt_events";
    $lessonsView=$wpdb->prefix."utt_lessons_view";

    $sql = "CREATE TABLE IF NOT EXISTS `$periodsTable` (
            `periodID` INT UNSIGNED NOT NULL AUTO_INCREMENT,
            `year` YEAR NOT NULL COMMENT 'το έτος - έτσι θα μπορεί να κρατηθεί και ιστορικό σε βάθος χρόνου',
            `semester` ENUM('Ε','Χ') NOT NULL COMMENT 'Εαρινό, Χειμερινό',
            PRIMARY KEY (`periodID`))
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$subjectsTable` (
            `subjectID` INT UNSIGNED NOT NULL AUTO_INCREMENT,
            `title` VARCHAR(64) NOT NULL COMMENT 'το επίσημο όνομα του μαθήματος',
            `type` ENUM('Θ','Ε','ΑΠ') NOT NULL COMMENT 'Θεωρία, Εργαστήριο, Άσκηση-Πράξη',
            `semester` TINYINT UNSIGNED NOT NULL COMMENT 'το εξάμηνο σπουδών στο οποίο απευθύνεται το μάθημα',
            `is_enabled` TINYINT(1) NOT NULL DEFAULT 1 COMMENT 'εαν το μάθημα είναι ενεργό - η εφαρμογή θα προβάλει μόνο τα ενεργά μαθήματα',
            `color` VARCHAR(45) NOT NULL COMMENT 'Το χρώμα που θα εμφανίζεται στο πρόγραμμα.',
            PRIMARY KEY (`subjectID`))
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$groupsTable` (
            `groupID` INT UNSIGNED NOT NULL AUTO_INCREMENT COMMENT 'μοναδικό μέσω ευρετηρίου UQ - για χρήση ως FKey στον Lessons',
            `periodID` INT UNSIGNED NOT NULL COMMENT 'FKey από Periods',
            `subjectID` INT UNSIGNED NOT NULL COMMENT 'FKey από Subjects',
            `groupName` VARCHAR(20) NOT NULL COMMENT 'το όνομα της ομάδας (εργαστηριακής, κτλ)',
            PRIMARY KEY (`periodID`, `subjectID`, `groupName`),
            INDEX `fk_Groups_Periods_idx` (`periodID` ASC),
            INDEX `fk_Groups_Subject1_idx` (`subjectID` ASC),
            UNIQUE INDEX `groupID_UNIQUE` (`groupID` ASC),
            CONSTRAINT `fk_Groups_Periods`
            FOREIGN KEY (`periodID`)
            REFERENCES `$periodsTable` (`periodID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE,
            CONSTRAINT `fk_Groups_Subjects`
            FOREIGN KEY (`subjectID`)
            REFERENCES `$subjectsTable` (`subjectID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE)
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$teachersTable` (
            `teacherID` SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
            `surname` VARCHAR(35) NOT NULL,
            `name` VARCHAR(35) NULL,
            PRIMARY KEY (`teacherID`))
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$classroomsTable` (
            `classroomID` SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
            `name` VARCHAR(35) NOT NULL,
            `type` ENUM('Δ','Ε') NOT NULL COMMENT 'Διαλέξεων, Εργαστηρίου',
            `is_available` TINYINT(1) NOT NULL DEFAULT 1,
            PRIMARY KEY (`classroomID`))
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$lessonsTable` (
            `lessonID` INT UNSIGNED NOT NULL AUTO_INCREMENT,
            `groupID` INT UNSIGNED NOT NULL COMMENT 'FKey από Groups',
            `classroomID` SMALLINT UNSIGNED NOT NULL COMMENT 'FKey από Classrooms',
            `teacherID` SMALLINT UNSIGNED NOT NULL COMMENT 'FKey από Teachers',
            `start` DATETIME NOT NULL COMMENT 'το date part καθορίζει την ημερομηνία και το time part την ώρα έναρξης',
            `end` DATETIME NOT NULL,
            INDEX `fk_Lesson_Classrooms1_idx` (`classroomID` ASC),
            INDEX `fk_Lesson_Teachers1_idx` (`teacherID` ASC),
            PRIMARY KEY (`lessonID`),
            CONSTRAINT `fk_Lessons_Classrooms`
            FOREIGN KEY (`classroomID`)
            REFERENCES `$classroomsTable` (`classroomID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE,
            CONSTRAINT `fk_Lessons_Teachers`
            FOREIGN KEY (`teacherID`)
            REFERENCES `$teachersTable` (`teacherID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE,
            CONSTRAINT `fk_Lessons_Groups1`
            FOREIGN KEY (`groupID`)
            REFERENCES `$groupsTable` (`groupID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE)
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";

    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$holidaysTable` (
            `holidayDate` DATE NOT NULL,
            `holidayName` VARCHAR(45) NOT NULL,
            PRIMARY KEY (`holidayDate`))
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $sql="CREATE TABLE IF NOT EXISTS `$eventsTable` (
            `eventID` INT UNSIGNED NOT NULL AUTO_INCREMENT,
            `eventType` VARCHAR(45) NOT NULL COMMENT 'Τύπος του συμβάντος.',
            `eventTitle` VARCHAR(45) NOT NULL COMMENT 'Τίτλος του συμβάντος',
            `eventDescr` VARCHAR(255) NULL COMMENT 'Περιγραφή του συμβάντος.',
            `classroomID` SMALLINT UNSIGNED NOT NULL COMMENT 'Fkey από classrooms',
            `eventStart` DATETIME NOT NULL COMMENT 'Ημερομηνία - ώρα που αρχίζει το συμβάν.',
            `eventEnd` DATETIME NOT NULL COMMENT 'Ημερομηνία - ώρα που τελειώνει το συμβάν.',
            PRIMARY KEY (`eventID`),
            INDEX `fk_wp_utt_events_wp_utt_classrooms1_idx` (`classroomID` ASC),
            CONSTRAINT `fk_wp_utt_events_wp_utt_classrooms1`
            FOREIGN KEY (`classroomID`)
            REFERENCES `$classroomsTable` (`classroomID`)
            ON DELETE RESTRICT
            ON UPDATE CASCADE)
            ENGINE = InnoDB
            DEFAULT CHARACTER SET = utf8
            COLLATE = utf8_general_ci;";
    dbDelta($sql);

    $wpdb->query("CREATE  OR REPLACE VIEW $lessonsView AS
            SELECT
                periodID,
                lessonID,
                semester,
                $lessonsTable.groupID,
                $lessonsTable.classroomID,
                $lessonsTable.teacherID,
                start,
                end,
                groupName,
                $subjectsTable.subjectID,
                $subjectsTable.title AS subjectTitle,
                $subjectsTable.type AS subjectType,
                color,
                $classroomsTable.name AS classroomName,
                $classroomsTable.type AS classroomType,
                surname as teacherSurname,
                $teachersTable.name as teacherName
            FROM
                $lessonsTable,
                $groupsTable,
                $subjectsTable,
                $classroomsTable,
                $teachersTable
            WHERE
                $lessonsTable.groupID = $groupsTable.groupID
                    AND $groupsTable.subjectID = $subjectsTable.subjectID
                    AND $lessonsTable.classroomID = $classroomsTable.classroomID
                    AND $lessonsTable.teacherID = $teachersTable.teacherID;");

}

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问题是，在更新到wordpress 4.2之后，wordpress不接受Accords和enum类型中的希腊字符。我必须让他们成为英国人

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我回答是为了帮助任何有同样问题的人

有人知道怎么回事吗？？？