-- 在目标主库执行；只增加启动页字段，不修改已有业务数据，可重复执行。
SET @ddl = IF(
    (SELECT COUNT(*) FROM information_schema.COLUMNS
     WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'tcm_system_settings'
       AND COLUMN_NAME = 'startup_page_enabled') = 0,
    'ALTER TABLE tcm_system_settings ADD COLUMN startup_page_enabled TINYINT(1) NOT NULL DEFAULT 0',
    'SELECT 1');
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET @ddl = IF(
    (SELECT COUNT(*) FROM information_schema.COLUMNS
     WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'tcm_system_settings'
       AND COLUMN_NAME = 'startup_page_image_url') = 0,
    'ALTER TABLE tcm_system_settings ADD COLUMN startup_page_image_url VARCHAR(1024) NOT NULL DEFAULT ''''',
    'SELECT 1');
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;