Question

我想知道是否有办法根据该请求优化视图：

SELECT product ,
  price ,
  quantity_in_stock ,
  location
FROM mytableA x
WHERE x.price =
  (SELECT MAX( z.price )
  FROM mytableA z
  WHERE (z.quantity_in_stock > 0)
  AND z.product          = x.product
  );

谢谢。

Answer 1

使用分析函数（单表扫描）而不是相关的子查询（两个表扫描）：

SELECT product,
       price,
       quantity_in_stock,
       location
FROM   (
  SELECT product,
         price,
         quantity_in_stock,
         location,
         MAX( CASE WHEN quantity_in_stock > 0 THEN price END ) OVER ( PARTITION BY product ) AS max_price_in_stock
  FROM   MyTable
)
WHERE price = max_price_in_stock;

[Oracle]优化查询包含最大子查询

1 个答案: