更新invoices表
    UPDATE invoices
    SET payment_total = 10, payment_date = ‘2019-03-01’
    WHERE invoice_id = 1

    使用默认值更新
    UPDATE invoices
    SET payment_total = DEFAULT, payment_date = NULL
    WHERE invoice_id = 1

    使用计算值更新
    UPDATE invoices
    SET
    payment_total = invoice_total * 0.5,
    payment_date = due_date
    WHERE invoice_id = 3