MySQL 根据条件多值更新的实现

UPDATE 表名
SET 
    字段1 = CASE 
        WHEN 条件1 THEN 值1
        WHEN 条件2 THEN 值2
        ELSE 字段1 
    END,
    字段2 = CASE 
        WHEN 条件1 THEN 值3
        WHEN 条件2 THEN 值4
        ELSE 字段2
    END
WHERE 整体过滤条件;

 
UPDATE products
SET
    stock = CASE 
        WHEN category_id = 5 AND price > 100 THEN stock - 10
        WHEN create_date < '2024-01-01' THEN stock + 5
        ELSE stock
    END,
    price = CASE 
        WHEN category_id = 5 THEN price * 0.9
        WHEN stock > 1000 THEN price * 0.8
        ELSE price
    END
WHERE status = 'active';

UPDATE users
SET 
    vip_level = CASE
        WHEN score >= 1000 THEN 'Diamond'
        WHEN score >= 500 THEN 'Gold'
        ELSE vip_level
    END,
    discount = CASE 
        WHEN score >= 1000 THEN 0.7
        WHEN score >= 500 THEN 0.8
        ELSE discount
    END
WHERE registration_year = 2024;

UPDATE orders o
JOIN payments p ON o.id = p.order_id
SET 
    o.status = CASE 
        WHEN p.paid = 1 THEN 'completed'
        ELSE 'pending'
    END,
    p.processed_at = NOW()
WHERE o.create_date > '2024-06-01';

UPDATE employees
SET
    salary = IF(performance > 90, salary * 1.2, salary),
    bonus = IF(join_year < 2020, bonus + 5000, bonus)
WHERE department = 'Engineering';