Question

我目前有以下查询：

WITH instances AS (
    SELECT b.ldtc as date, a.fk_item_id, b.movement, a.quantity, 
        CASE WHEN b.movement = 'Inbound' THEN a.quantity ELSE -a.quantity END as absquantity
    FROM inventory_resupplylogiteminstance a
    INNER JOIN inventory_resupplylog b ON b.uid = a.fk_resupply_log_id
)

SELECT a.name, 
    SUM(CASE WHEN b.date < ('2018-10-10'::date) THEN b.absquantity END) as starting_balance,

    SUM(CASE WHEN b.date > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date) AND b.movement = 'aa' THEN b.absquantity END) as aa,
    SUM(CASE WHEN b.date > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date) AND b.movement = 'bb' THEN b.absquantity END) as bb,
    SUM(CASE WHEN b.date > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date) AND b.movement = 'cc' THEN b.absquantity END) as cc,
    SUM(CASE WHEN b.date > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date) AND b.movement = 'dd' THEN b.absquantity END) as dd,

    SUM(CASE WHEN b.date < ('2018-10-12'::date) THEN b.absquantity END) AS ending_balance




FROM inventory_item a
LEFT JOIN instances b ON b.fk_item_id = a.uid

GROUP BY a.uid, a.name
ORDER BY a.name

如您所见，第2-5行SUM行是多余的，因为它们正在查询b.date与2018-10-10之间的行。有什么方法可以重写我的查询，以便只写一次2018-10-12并仍然能够在同一行上选择b.date > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date)和starting_balance？

Answer 1

您可以检查CTE中的范围，并创建一个标志来指示该行是否在指定的范围内。

然后，您可以在最终的SELECT中使用该标志。切换到FILTER ()表达式也使其更具可读性：

WITH instances AS (
  SELECT b.ldtc as date, 
         a.fk_item_id, 
         b.movement, 
         a.quantity, 
         CASE 
           WHEN b.movement = 'Inbound' THEN a.quantity 
           ELSE -a.quantity 
         END as absquantity,
         -- the column in_range returns either true or false
         (b.ldtc > ('2018-10-10'::date) AND b.date < ('2018-10-12'::date)) as in_range
  FROM inventory_resupplylogiteminstance a
    INNER JOIN inventory_resupplylog b ON b.uid = a.fk_resupply_log_id
)
SELECT a.name, 
       SUM(b.absquantity) filter (where b.date < '2018-10-10'::date) as starting_balance,
       SUM(b.absquantity) filter (where in_range and b.movement = 'aa') as aa,
       SUM(b.absquantity) filter (where in_range and b.movement = 'bb') as bb,
       SUM(b.absquantity) filter (where in_range and b.movement = 'cc') as cc,
       SUM(b.absquantity) filter (where in_range and b.movement = 'dd') as dd,
       SUM(b.absquantity) filter (where b.date < '2018-10-12'::date) AS ending_balance
FROM inventory_item a
  LEFT JOIN instances b ON b.fk_item_id = a.uid
GROUP BY a.uid, a.name
ORDER BY a.name;

如果您也不想重复开始和结束余额的日期，则可以将要测试的范围放入CTE，然后在最终查询中使用Postgres的range functions：< / p>

WITH instances AS (
  SELECT b.ldtc as date, 
         a.fk_item_id, 
         b.movement, 
         a.quantity, 
         CASE 
           WHEN b.movement = 'Inbound' THEN a.quantity 
           ELSE -a.quantity 
         END as absquantity,
         daterange('2018-10-10'::date, '2018-10-12'::date, '()') as check_range
  FROM inventory_resupplylogiteminstance a
    INNER JOIN inventory_resupplylog b ON b.uid = a.fk_resupply_log_id
)
SELECT a.name, 
    SUM(b.absquantity) filter (where b.date < lower(check_range)) as starting_balance,
    SUM(b.absquantity) filter (where b.date <@ b.check_range and b.movement = 'aa') as aa,
    SUM(b.absquantity) filter (where b.date <@ b.check_range and b.movement = 'bb') as bb,
    SUM(b.absquantity) filter (where b.date <@ b.check_range and b.movement = 'cc') as cc,
    SUM(b.absquantity) filter (where b.date <@ b.check_range and b.movement = 'dd') as dd,
    SUM(b.absquantity) filter (where b.date < upper(b.check_range))) AS ending_balance
FROM inventory_item a
  LEFT JOIN instances b ON b.fk_item_id = a.uid
GROUP BY a.uid, a.name
ORDER BY a.name;

daterange('2018-10-10'::date, '2018-10-12'::date, '()')创建一个date range，其中两个日期被排除。

<@运算符测试日期是否在给定范围内。

因此，表达式b.date <@ b.check_range与b.date > '2018-10-10'::date AND b.date < '2018-10-12'::date等效（因为定义的范围不包括边缘）

Postgres过滤WITH查询

1 个答案: