使用SQL查询检查序列

Question

我有一个表订单，可以保存我们所有商店的所有订单。 我写了一个查询来检查每个商店的序列顺序。 它看起来像那样。

select WebStoreID, min(webordernumber), max(webordernumber), count(webordernumber) 
from orders
where ordertype = 'WEB' 
group by WebStoreID

我可以查看此查询中是否存在所有订单。 web ordernumber是1 ... n。

中的数字

如何在不加入临时/不同表的情况下编写查询以查找丢失的订单？

Answer 1

您可以将表连接到自身以检测没有前一行的行：

select cur.*
from orders cur
left join orders prev 
    on cur.webordernumber = prev.webordernumber + 1
    and cur.webstoreid = prev.webstoreid
where cur.webordernumber <> 1
and prev.webordernumer is null

这将检测1 ... n序列中的间隙，但不会检测到重复。

Answer 2

我会创建一个“从1到n的所有整数”的辅助表。 （参见 http://www.sql-server-helper.com/函数/ integer-table.aspx 用于某些方法来使用SQL Server函数，但是因为它是你需要反复使用的东西，所以无论如何我都会把它变成一个真正的表，并且使用任何SQL引擎它很容易做到，只需一次）然后使用嵌套查询， SELECT值FROM整数WHERE值NOT IN（SELECT webordernumber FROM orders）＆amp; c。另请参阅 http://www.sqlmag.com/Article/ArticleID/99797/ sql_server_99797.html 针对与您类似的问题，“检测一系列数字中的差距”。

Answer 3

如果你有rank（）函数而不是lag（）函数（换句话说，SQL Server），你可以使用它（由 http://www.sqlmonster.com/Uwe/Forum.aspx/sql-server-programming / 10594 /返回隙-IN-A-序列）：

create table test_gaps_in_sequence (x int)
insert into test_gaps_in_sequence values ( 1 )
insert into test_gaps_in_sequence values ( 2 )
insert into test_gaps_in_sequence values ( 4 )
insert into test_gaps_in_sequence values ( 5 )
insert into test_gaps_in_sequence values ( 8 )
insert into test_gaps_in_sequence values ( 9 )
insert into test_gaps_in_sequence values ( 12)
insert into test_gaps_in_sequence values ( 13)
insert into test_gaps_in_sequence values ( 14)
insert into test_gaps_in_sequence values ( 29)

...

 select lower_bound
         , upper_bound
      from (select upper_bound
                 , rank () over (order by upper_bound) - 1 as upper_rank
              from (SELECT x+n as upper_bound
                      from test_gaps_in_sequence
                         , (SELECT 0 n
                            UNION
                            SELECT -1
                           ) T
                     GROUP BY x+n
                    HAVING MAX(n) = -1
                    ) upper_1
            ) upper_2
         , (select lower_bound
                 , rank () over (order by lower_bound) as lower_rank
              from (SELECT x+n as lower_bound
                      from test_gaps_in_sequence
                         , (SELECT 0 n
                            UNION
                            SELECT 1
                           ) T
                     GROUP BY x+n
                    HAVING MIN(n) = 1
                    ) lower_1
            ) lower_2
      where upper_2.upper_rank = lower_2.lower_rank
      order by lower_bound

...或者，包括“外部限制”：

select lower_bound
     , upper_bound
  from (select upper_bound
             , rank () over (order by upper_bound) - 1 as upper_rank
          from (SELECT x+n as upper_bound
                  from test_gaps_in_sequence
                     , (SELECT 0 n
                        UNION
                        SELECT -1
                       ) T
                 GROUP BY x+n
                HAVING MAX(n) = -1
                ) upper_1
        ) upper_2
   full join (select lower_bound
             , rank () over (order by lower_bound) as lower_rank
          from (SELECT x+n as lower_bound
                  from test_gaps_in_sequence
                     , (SELECT 0 n
                        UNION
                        SELECT 1
                       ) T
                 GROUP BY x+n
                HAVING MIN(n) = 1
                ) lower_1
        ) lower_2
   on upper_2.upper_rank  = lower_2.lower_rank
     order by coalesce (lower_bound, upper_bound)

Answer 4

如果您的数据库支持分析函数，那么您可以使用如下查询：

select prev+1, curr-1 from
( select webordernumber curr,
         coalesce (lag(webordernumber) over (order by webordernumber), 0) prev
  from   orders
)
where prev != curr-1;

输出将显示间隙，例如

prev+1 curr-1
------ ------
     3      7

意味着缺少3到7号的数字。