如何在不使用 UNION 进行单个 SQL 查询的情况下对超过 2 个 SQL 语句进行

Question

SELECT 'INITIALIZE' AS PROCESS_DESC,
  floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24)
  || ' HOURS '
  || mod(floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24*60),60)
  || ' MINUTES '
  || mod(floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24*60*60),60)
  || ' SECS ' time_difference
FROM spool_table
WHERE process_desc                         ='INITIALIZE'
AND to_date(EXEC_DATE, 'DD-MON-YYYY')      =
  (SELECT to_date(EXEC_DATE, 'DD-MON-YYYY')=
  FROM spool_table
  WHERE process_desc='INITIALIZE'
  )
UNION ALL
SELECT 'PRELIM' AS PROCESS_DESC,
  floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24)
  || ' HOURS '
  || mod(floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24*60),60)
  || ' MINUTES '
  || mod(floor((MAX(EXEC_DATE)-MIN(EXEC_DATE))*24*60*60),60)
  || ' SECS ' time_difference
FROM spool_table
WHERE process_desc                   ='PRELIM'
AND to_date(EXEC_DATE, 'DD-MON-YYYY')=
  (SELECT to_date(MAX(EXEC_DATE), 'DD-MON-YYYY')
  FROM spool_table
  WHERE process_desc='PRELIM'
  )

Answer 1

在这种情况下，

您可以使用 FIRST(或 LAST(来查找最新日期的最小日期时间：

with cte (process_desc, max_exec_date, min_exec_date) as (
    select 
        process_desc,
        max(exec_date) max_exec_date,
        min(exec_date) keep (dense_rank last order by trunc(exec_date) nulls first) min_exec_date
    from spool_table s
    where process_desc in ('PRELIM', 'INITIALIZE') -- include or exclude what process you want here
    group by process_desc
)
select
    process_desc,
    floor((max_exec_date-min_exec_date)*24) || ' HOURS ' ||
    mod(floor((max_exec_date-min_exec_date)*24*60),60)  || ' MINUTES ' ||
    mod(floor((max_exec_date-min_exec_date)*24*60*60),60) 
    || ' SECS ' time_difference
from cte;

CTE 在那里澄清查询。如果需要，您可以将其作为子查询放置，甚至可以不使用这样的子查询：

select
    process_desc,
    floor((max(exec_date)-min(exec_date) keep (dense_rank last order by trunc(exec_date) nulls first))*24) || ' HOURS ' ||
    mod(floor((max(exec_date)-min(exec_date) keep (dense_rank last order by trunc(exec_date) nulls first))*24*60),60)   || ' MINUTES ' ||
    mod(floor((max(exec_date)-min(exec_date) keep (dense_rank last order by trunc(exec_date) nulls first))*24*60*60),60) 
    || ' SECS ' time_difference
from spool_table s
where process_desc in ('PRELIM', 'INITIALIZE')
group by process_desc;

有点幼稚的方式是使用相关的子查询：

select process_desc,
  floor((max(exec_date)-min(exec_date))*24)
  || ' HOURS '
  || mod(floor((max(exec_date)-min(exec_date))*24*60),60)
  || ' MINUTES '
  || mod(floor((max(exec_date)-min(exec_date))*24*60*60),60)
  || ' SECS ' time_difference
from spool_table s
where process_desc in ('PRELIM', 'INITIALIZE')
and trunc(exec_date) = (
    select trunc(max(exec_date))
    from spool_table t
    where t.process_desc = s.process_desc
)
group by process_desc;