在 BigQuery 中从数组中减去项目

Question

我有一个查询，当用户向购物车添加商品时，它会跟踪购物车中的商品。我已经完成了添加项目的部分，但是我无法根据给定的操作删除单个项目。下面是一个例子：

SELECT
  *,
  -- Remove item from cart where item in cart
  CASE WHEN cart_action = 'remove from cart' THEN (SELECT SPLIT(cart, ',') - SPLIT(cart, ',') WHERE SPLIT(cart, ',') = item)
FROM
(
SELECT 
  'remove from cart' AS cart_action,
  'apple' AS item,
  'apple, orange, banana, apple' AS cart
  );

如果我的购物车以 开始'apple, orange, banana, apple'，那么我希望输出为'orange, banana, apple'。物品的顺序无关紧要。

我希望能够将购物车字符串分成一个数组，在数组中找到一个匹配的项目，删除该项目，然后返回更新后的购物车。

Answer 1

以下示例适用于 BigQuery 标准 SQL

#standardSQL
WITH `action` AS (
  SELECT 
    'remove from cart' AS cart_action,
    'apple' AS item,
    'apple, orange, banana, apple' AS cart
)
SELECT 
  *,
  (SELECT STRING_AGG(cart_item) 
    FROM UNNEST(SPLIT(cart)) cart_item 
    WHERE TRIM(cart_item) != item
  ) new_cart
FROM `action`

结果为

Row cart_action         item    cart                            new_cart     
1   remove from cart    apple   apple, orange, banana, apple    orange, banana, apple