SQL选择使日期时间范围在标记切换之间的项目

Question

说我有一个这样的表:

CREATE TABLE TESTTABLE (
  ID Integer NOT NULL,
  ATMOMENT Timestamp NOT NULL,
  ISALARM Integer NOT NULL,
  CONSTRAINT PK_TESTTABLE PRIMARY KEY (ID)
);

它具有ISALARM标志,可在随机时刻ATMOMENT之间切换0到1,就像在此示例数据集中一样:

INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('1', '01.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('2', '01.01.2016, 00:01:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('3', '01.01.2016, 00:02:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('4', '01.01.2016, 00:02:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('10', '02.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('11', '02.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('12', '02.01.2016, 00:01:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('20', '03.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('21', '03.01.2016, 00:01:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('22', '03.01.2016, 00:02:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('23', '03.01.2016, 00:02:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('30', '04.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('31', '04.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('32', '04.01.2016, 00:00:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('33', '04.01.2016, 00:00:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('40', '05.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('41', '05.01.2016, 00:00:00.000', '1');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('42', '05.01.2016, 00:00:00.000', '0');
INSERT INTO TESTTABLE (ID, ATMOMENT, ISALARM) VALUES ('43', '05.01.2016, 00:00:00.000', '0');

我需要选择所有报警范围,即ISAMARM设置为1的ATMOMENT范围(前一个范围关闭后第一次)在范围开始,并在范围结束时重置为0.为清楚起见,首先重置足以关闭此范围; 同时说同时ISALARM设置和重置被视为范围结束(可能作为开始).上面的示例数据集预计会生成如下内容:

 ALARMBEGIN                |  LASTALARMBEGIN            |  ALARMEND
-------------------------- | -------------------------- | --------
'01.01.2016, 00:00:00.000' | '01.01.2016, 00:01:00.000' | '01.01.2016, 00:02:00.000'
'02.01.2016, 00:00:00.000' | '02.01.2016, 00:00:00.000' | '02.01.2016, 00:01:00.000'
'03.01.2016, 00:00:00.000' | '03.01.2016, 00:02:00.000' | '03.01.2016, 00:02:00.000'
'04.01.2016, 00:00:00.000' | '04.01.2016, 00:00:00.000' | '04.01.2016, 00:00:00.000'
'05.01.2016, 00:00:00.000' | '05.01.2016, 00:00:00.000' | '05.01.2016, 00:00:00.000'

我自己的解决方案(下图)看起来非常难看并且运行速度非常慢(大约1分钟),即使TESTTABLE具有相对较小的数据集,只有大约2500条记录(使用Firebird2.5和Postgresql进行测试;我对数据库优化不太好;"在TESTTABLE(ATMOMENT,ISALARM)上创建索引IDX_TESTTABLE1"有帮助,但不是很多).

这对我来说很奇怪,因为在将ISALARM字段与之前的记录之一进行比较时,对所有TESTTABLE记录(由ATMOMENT排序)进行简单的线性迭代,可以得到我想要的范围更快.

有没有优雅的解决方案让SQL更快更清洁地选择？

SELECT DISTINCT a1.ATMOMENT AS ALARMBEGIN, a2.ATMOMENT AS LASTALARMBEGIN, a3.ATMOMENT AS ALARMEND
FROM TESTTABLE a1
JOIN TESTTABLE a2 ON 
    (a1.ATMOMENT<a2.ATMOMENT
        AND NOT EXISTS(SELECT * FROM TESTTABLE x WHERE 
            x.ISALARM=0 AND a1.ATMOMENT<=x.ATMOMENT AND x.ATMOMENT<a2.ATMOMENT))
    OR (a1.ATMOMENT=a2.ATMOMENT)
JOIN TESTTABLE a3 ON 
    (a2.ATMOMENT<a3.ATMOMENT
        AND NOT EXISTS(SELECT * FROM TESTTABLE x WHERE 
            (x.ISALARM=0 AND a2.ATMOMENT<=x.ATMOMENT AND x.ATMOMENT<a3.ATMOMENT)
            OR (x.ISALARM=1 AND a2.ATMOMENT<x.ATMOMENT AND x.ATMOMENT<=a3.ATMOMENT)))
    OR (a2.ATMOMENT=a3.ATMOMENT)
WHERE a1.ISALARM<>0 AND a2.ISALARM<>0 AND a3.ISALARM=0
    AND (NOT EXISTS(SELECT * FROM TESTTABLE x1 WHERE
            x1.ATMOMENT<a1.ATMOMENT)
        OR EXISTS(SELECT * FROM TESTTABLE x1 WHERE
            x1.ISALARM=0
            AND x1.ATMOMENT<a1.ATMOMENT
            AND NOT EXISTS(SELECT * FROM TESTTABLE x2 WHERE
                x1.ATMOMENT<x2.ATMOMENT AND x2.ATMOMENT<a1.ATMOMENT)))
ORDER BY a1.ATMOMENT

谢谢.

更新1

感谢Gordon Linoff和Jayvee的解决方案(Firebird3.0和PostgreSQL非常好),我决定依靠Firebird2.5的订购效率并设计出"选择",它比我之前的更好,但运行得更快.对于那些需要使用Firebird2.5完成的人:

WITH 
GROUPEDTABLE_TT (ATMOMENT, NOTISALARMRESET, ISALARMSET)
AS(
SELECT a.ATMOMENT, MIN(a.ISALARM), MAX(a.ISALARM)
FROM TESTTABLE a
GROUP BY a.ATMOMENT),

INTERVALBEGIN_TT 
AS(
SELECT a1.ATMOMENT
FROM GROUPEDTABLE_TT a1
WHERE 
    a1.ISALARMSET<>0
    AND (NOT EXISTS (SELECT * FROM GROUPEDTABLE_TT x WHERE
            x.ATMOMENT<a1.ATMOMENT)
        OR (SELECT FIRST 1 x.NOTISALARMRESET FROM GROUPEDTABLE_TT x WHERE
            x.ATMOMENT<a1.ATMOMENT
            ORDER BY x.ATMOMENT DESC)=0)),

INTERVALLAST_TT 
AS(
SELECT a2.ATMOMENT FROM GROUPEDTABLE_TT a2
WHERE a2.ISALARMSET=1
    AND (a2.NOTISALARMRESET=0
        OR (a2.NOTISALARMRESET=1 
            AND (SELECT FIRST 1 x.NOTISALARMRESET FROM GROUPEDTABLE_TT x WHERE
                x.ATMOMENT>a2.ATMOMENT
                ORDER BY x.ATMOMENT ASC)=0
            AND (SELECT FIRST 1 x.ISALARMSET FROM GROUPEDTABLE_TT x WHERE
                x.ATMOMENT>a2.ATMOMENT
                ORDER BY x.ATMOMENT ASC)=0))),

INTERVALEND_TT 
AS(
SELECT a1.ATMOMENT
FROM GROUPEDTABLE_TT a1
WHERE 
    a1.NOTISALARMRESET=0
    AND (a1.ISALARMSET=1 
        OR (a1.ISALARMSET=0 
            AND (SELECT FIRST 1 x.ISALARMSET FROM GROUPEDTABLE_TT x WHERE
                x.ATMOMENT<a1.ATMOMENT
                ORDER BY x.ATMOMENT DESC)=1
            AND (SELECT FIRST 1 x.NOTISALARMRESET FROM GROUPEDTABLE_TT x WHERE
                x.ATMOMENT<a1.ATMOMENT
                ORDER BY x.ATMOMENT DESC)=1))),

ENCLOSEDINTERVALS_TT (BEGINMOMENT, LASTBEGINMOMENT, ENDMOMENT)
AS(
SELECT ib.ATMOMENT, 
    (SELECT FIRST 1 il.ATMOMENT FROM INTERVALLAST_TT il WHERE 
        ib.ATMOMENT<=il.ATMOMENT ORDER BY il.ATMOMENT ASC),
    (SELECT FIRST 1 ie.ATMOMENT FROM INTERVALEND_TT ie WHERE 
        ib.ATMOMENT<=ie.ATMOMENT ORDER BY ie.ATMOMENT ASC)
FROM INTERVALBEGIN_TT ib)

SELECT * FROM ENCLOSEDINTERVALS_TT
ORDER BY BEGINMOMENT

更新2 ...但我的选择似乎显示取决于总记录数的取数的二次增长(或至少快于线性); 对于FB2.5,最好使用单程线性迭代的程序.或者使用FB30以下解决方案......

Answer 1

我认为你可以在 Firebird 3.0 中使用以下命令来做到这一点row_number()：

select alarm, min(atmoment), max(atmoment)
from (select t.*,
             row_number() over (order by atmoment) as seqnum,
             row_number() over (partition by alarm order by atmoment) as seqnum_a
      from testtable t
     ) t
group by alarm, (seqnum - seqnum_a);

解释它是如何工作的有点困难。但如果您运行子查询，您将看到差异如何识别您感兴趣的组。