SQL相当于python for循环

Question

我觉得必须有一种方法可以直接在 SQL 中完成这个 for 循环。有人可以指导一下吗？

for x in range(1, numckts + 1, 6):
      alist.append(x)
      alist.append(x + 1)

for val in alist:
    sql = (
        "SELECT VA FROM circuits WHERE pnl_id = "
        + pnlid
        + " AND Num = "
        + str(val)
        + ";"
    )
    rows = cur.execute(sql)
    for row in rows:
        valA = valA + row[0]

Answer 1

select p.pnlid
, c.Num
, c.VA
from circuits c
  inner join panel p on p.pnlid = c.pnl_id
where (c.Num % 6) in (1, 2)

Answer 2

考虑 SQLite 中的 ROW_NUMBER() window function 以按顺序计算每个 pnl_id 中的行数。然后，每 6 行（即第 7 行和第 8 行）之后使用模运算符查找连接，以过滤最终聚合。

请注意：对于可能随 Python 3.8.x 一起提供的窗口函数，您需要 SQLite 版本至少为 3.25。请与sqlite3.sqlite_version联系。

WITH sub_row AS 
   (SELECT ROW_NUMBER() OVER(PARTITION BY c.pnl_id ORDER BY rowid) AS rn
           , c.pnl_id
           , c.[VA]
           , p. numckts
    FROM circuits c
    INNER JOIN panelboards p
           ON c.pnl_id = p.id)
    , 
     sub_conn AS
   (SELECT rn
           , CASE WHEN rn % 6 IN (1, 2) THEN 1 ELSE 0 END) AS conn           
           , pnl_id
           , [VA]
           , numckts
    FROM sub_row
    WHERE rn < numckts + 1)

SELECT pnl_id, SUM(VA) AS sum_VA
FROM sub_conn
WHERE conn = 1
GROUP BY pnl_id