DO $$ 
BEGIN
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'products' AND column_name = 'color') THEN
        ALTER TABLE products ADD COLUMN color VARCHAR(50);
    END IF;
    
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'products' AND column_name = 'material') THEN
        ALTER TABLE products ADD COLUMN material VARCHAR(100);
    END IF;
    
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'products' AND column_name = 'card_size') THEN
        ALTER TABLE products ADD COLUMN card_size VARCHAR(20) DEFAULT 'small';
    END IF;
END $$;

DO $$ 
BEGIN
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'users' AND column_name = 'city') THEN
        ALTER TABLE users ADD COLUMN city VARCHAR(100);
    END IF;
    
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'users' AND column_name = 'last_login') THEN
        ALTER TABLE users ADD COLUMN last_login TIMESTAMP;
    END IF;
END $$;

DO $$ 
BEGIN
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'categories' AND column_name = 'updated_at') THEN
        ALTER TABLE categories ADD COLUMN updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
    END IF;
    
    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
                   WHERE table_name = 'categories' AND column_name = 'created_at') THEN
        ALTER TABLE categories ADD COLUMN created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP;
    END IF;
END $$;