SELECT...DATA_VALUE =
(CASE SAMPLE_START_TIME
   WHEN '0' THEN CONT_HOUR1_VALUE
   WHEN '100'....
   ....
END),
DATA_FLAG =
((CASE SAMPLE_START_TIME
   WHEN '0' THEN CONT_HOUR1_FLAG
   WHEN '100'....
   ....
END)

DECLARE @sdate_start datetime
       ,@sdate_end datetime
select @sdate_start = '01-Jul-1988'
       ,@sdate_end = '31-Dec-1988'

declare @dates table (sdate datetime)

insert @dates (sdate)
select dateadd(day, number, @sdate_start)
from   master..spt_values
where  type = 'P'
and    number < datediff(day, @sdate_start, @sdate_end)

INSERT INTO PLOT_DATA 
       (DATA_SAMPLE_NUM
       ,DATA_PARAMETER
       ,DATA_METHOD
       ,DATA_UNIT
       ,DATA_DECIMAL
       ,DATA_VALUE
       ,DATA_FLAG)

SELECT [TSAMPLE_NUM]
       ,[CONT_PARAMETER]
       ,[CONT_METHOD]
       ,[CONT_UNITS]
       ,[CONT_DECIMAL]
       ,TDATA_VALUE =
              CASE TSAMPLE_START_TIME
              WHEN '0' THEN CONT_HOUR1_VALUE
              WHEN '100' THEN CONT_HOUR2_VALUE
              WHEN '200' THEN CONT_HOUR3_VALUE
              WHEN '300' THEN CONT_HOUR4_VALUE
              WHEN '400' THEN CONT_HOUR5_VALUE
              WHEN '500' THEN CONT_HOUR6_VALUE
              WHEN '600' THEN CONT_HOUR7_VALUE
              WHEN '700' THEN CONT_HOUR8_VALUE
              WHEN '800' THEN CONT_HOUR9_VALUE
              WHEN '900' THEN CONT_HOUR10_VALUE
              WHEN '1000' THEN CONT_HOUR11_VALUE
              WHEN '1100' THEN CONT_HOUR12_VALUE
              WHEN '1200' THEN CONT_HOUR13_VALUE
              WHEN '1300' THEN CONT_HOUR14_VALUE
              WHEN '1400' THEN CONT_HOUR15_VALUE
              WHEN '1500' THEN CONT_HOUR16_VALUE
              WHEN '1600' THEN CONT_HOUR17_VALUE
              WHEN '1700' THEN CONT_HOUR18_VALUE
              WHEN '1800' THEN CONT_HOUR19_VALUE
              WHEN '1900' THEN CONT_HOUR20_VALUE
              WHEN '2000' THEN CONT_HOUR21_VALUE
              WHEN '2100' THEN CONT_HOUR22_VALUE
              WHEN '2200' THEN CONT_HOUR23_VALUE
              WHEN '2300' THEN CONT_HOUR24_VALUE
              END
       ,TDATA_FLAG =
              CASE TSAMPLE_START_TIME
              WHEN '0' THEN CONT_HOUR1_FLAG
              WHEN '100' THEN CONT_HOUR2_FLAG
              WHEN '200' THEN CONT_HOUR3_FLAG
              WHEN '300' THEN CONT_HOUR4_FLAG
              WHEN '400' THEN CONT_HOUR5_FLAG
              WHEN '500' THEN CONT_HOUR6_FLAG
              WHEN '600' THEN CONT_HOUR7_FLAG
              WHEN '700' THEN CONT_HOUR8_FLAG
              WHEN '800' THEN CONT_HOUR9_FLAG
              WHEN '900' THEN CONT_HOUR10_FLAG
              WHEN '1000' THEN CONT_HOUR11_FLAG
              WHEN '1100' THEN CONT_HOUR12_FLAG
              WHEN '1200' THEN CONT_HOUR13_FLAG
              WHEN '1300' THEN CONT_HOUR14_FLAG
              WHEN '1400' THEN CONT_HOUR15_FLAG
              WHEN '1500' THEN CONT_HOUR16_FLAG
              WHEN '1600' THEN CONT_HOUR17_FLAG
              WHEN '1700' THEN CONT_HOUR18_FLAG
              WHEN '1800' THEN CONT_HOUR19_FLAG
              WHEN '1900' THEN CONT_HOUR20_FLAG
              WHEN '2000' THEN CONT_HOUR21_FLAG
              WHEN '2100' THEN CONT_HOUR22_FLAG
              WHEN '2200' THEN CONT_HOUR23_FLAG
              WHEN '2300' THEN CONT_HOUR24_FLAG
              END

FROM   PLOT_DATA_TEMP
inner join CONTINUOUS_DATA 
       on TSAMPLE_OLD_NUM = CONT_SAMPLE_NUM
inner join @dates d
       on d.sdate = TSAMPLE_START_DATE

ORDER BY TSAMPLE_NUM
       ,CONT_PARAMETER,CONT_METHOD