sql - 跨 SQL 集合操作的 WHERE 子句

Question

考虑以下查询，其中两个集合都需要由相同的Location. 是否有一种更有效/性能更高的方法，即Location过滤器仅在两组中应用一次，或者您是否被迫将相同的过滤器单独应用于每个组？

SELECT *
FROM   Orders
WHERE  Quantity BETWEEN 1 AND 100
AND Location = 'SE'

EXCEPT

SELECT *
FROM   Orders
WHERE  Quantity BETWEEN 50 AND 75
AND Location = 'SE';

注意：不打算重构集合操作本身 - 这只是一个虚拟示例。我的问题只是关于如何跨集合操作处理常见的 WHERE 子句。

Answer 1

我会将查询重新分解为：

SELECT *
FROM Orders
WHERE Quantity BETWEEN 1 AND 100
AND Quantity NOT BETWEEN 50 AND 75
AND Location = 'SE';

Answer 2

您可以使用 AND NOT 代替 EXCEPT [ 1 ] 来处理集合操作，在不同平台上获得更大的支持。

我觉得有一点值得一提，总结一下：

1. 把最不可能的表达放在第一位。
2. 将最不复杂的表达式放在首位。
3. 使用更多和更少的搜索。

如果由于从右到左的评估而不是从左到右的评估而使用 Oracle，则颠倒第 1 点和第 2 点。

Answer 3

You can do this with a CTE:

with ord (Column1, Column2) as
(
    SELECT Column1, Column2
    FROM Orders 
    WHERE Location = 'SE'
)
SELECT *
FROM ord
WHERE Quantity BETWEEN 1 AND 100

EXCEPT

SELECT *
FROM ord
WHERE Quantity BETWEEN 50 AND 75

If CTEs are not available, you could do the same thing with a view.

Answer 4

SELECT *
FROM   Orders
WHERE  ((Quantity BETWEEN 1 AND 49) OR (Quantity BETWEEN 76 AND 100))
AND Location = 'SE'

试试这个查询并确保它获取相同的结果。

Answer 5

我会这样做：

SELECT *
FROM   Orders
WHERE  ((Quantity BETWEEN 1 AND 49)
OR (Quantity BETWEEN 76 AND 100))
AND Location = 'SE';

Answer 6

SELECT * 
FROM   Orders o1
WHERE  Quantity BETWEEN 1 AND 100 
AND Location = 'SE'
AND NOT EXISTS ( SELECT 1 FROM ORDERS o2 
                 WHERE QUANTITY BETWEEN 50 AND 75 
                 AND Location = 'SE' 
                 AND o1.ORDERS_ID = o2.ORDERS_ID)