CREATE TABLE `Ref_Characteristic_Types` (
`characteristic_type_code` VARCHAR(15) PRIMARY KEY,
`characteristic_type_description` VARCHAR(80)
)

CREATE TABLE `Ref_Colors` (
`color_code` VARCHAR(15) PRIMARY KEY,
`color_description` VARCHAR(80)
)

CREATE TABLE `Ref_Product_Categories` (
`product_category_code` VARCHAR(15) PRIMARY KEY,
`product_category_description` VARCHAR(80),
`unit_of_measure` VARCHAR(20)
)

CREATE TABLE `Characteristics` (
`characteristic_id` INTEGER PRIMARY KEY,
`characteristic_type_code` VARCHAR(15) NOT NULL,
`characteristic_data_type` VARCHAR(10),
`characteristic_name` VARCHAR(80),
`other_characteristic_details` VARCHAR(255),
FOREIGN KEY (`characteristic_type_code` ) REFERENCES `Ref_Characteristic_Types`(`characteristic_type_code` )
)

CREATE TABLE `Products` (
`product_id` INTEGER PRIMARY KEY,
`color_code` VARCHAR(15) NOT NULL,
`product_category_code` VARCHAR(15) NOT NULL,
`product_name` VARCHAR(80),
`typical_buying_price` VARCHAR(20),
`typical_selling_price` VARCHAR(20),
`product_description` VARCHAR(255),
`other_product_details` VARCHAR(255),
FOREIGN KEY (`product_category_code` ) REFERENCES `Ref_Product_Categories`(`product_category_code` ),FOREIGN KEY (`color_code` ) REFERENCES `Ref_Colors`(`color_code` )
)

CREATE TABLE `Product_Characteristics` (
`product_id` INTEGER NOT NULL,
`characteristic_id` INTEGER NOT NULL,
`product_characteristic_value` VARCHAR(50),
FOREIGN KEY (`characteristic_id` ) REFERENCES `Characteristics`(`characteristic_id` ),
FOREIGN KEY (`product_id` ) REFERENCES `Products`(`product_id` )
)
SELECT t3.characteristic_name FROM products AS t1 JOIN product_characteristics AS t2 ON t1.product_id  =  t2.product_id JOIN CHARACTERISTICS AS t3 ON t2.characteristic_id  =  t3.characteristic_id GROUP BY t3.characteristic_name HAVING count(*)  >= 2
Give the names of characteristics that are in two or more products?