[英]Count, Having and Case statement
我希望根據3種不同的條件(DB2數據庫)生成一系列項目。 我需要計算所有項目<=。10,> = .5和> = 1.00(percentage_used),但只能按dim_building_id和building_name進行分組。 當然,此查詢不會運行,因為它需要將percentage_used添加到組中。 如何使用percentage_used處理這3個條件?
SELECT
SUM(CAST(FTS.GROUP_A AS BIGINT)) AS GROUP_A,
SUM(CAST(FTS.GROUP_B AS BIGINT)) AS GROUP_B,
SUM(CAST(FTS.GROUP_C AS BIGINT)) AS GROUP_C,
CASE WHEN FAT.PERCENTAGE_USED <= '0.10'
THEN COUNT(*)
END AS PROJECTS_L10,
CASE WHEN FAT.PERCENTAGE_USED >= '0.50'
THEN COUNT(*)
END AS PROJECTS_G50,
CASE WHEN FAT.PERCENTAGE_USED >= '1.00'
THEN COUNT(*)
END AS PROJECTS_G100,
DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE) AS DAYS_LEFT,
(DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE))/7 AS WEEKS_LEFT,
DAYS(DATE('2013-12-31')) - DAYS(CURRENT DATE) AS DAYS_LEFT_YEAR
FROM FACT_TABLE AS FAT
INNER JOIN GROUPS AS FTS ON FAT.DIM_PROJECT_ID = FTS.DIM_PROJECT_ID
GROUP BY FAT.DIM_BUILDING_ID, FAT.BUILDING_NAME;
而不是將聚合作為THEN
,將CASE
語句包裝在聚合中:
SELECT
SUM(CAST(FTS.GROUP_A AS BIGINT)) AS GROUP_A,
SUM(CAST(FTS.GROUP_B AS BIGINT)) AS GROUP_B,
SUM(CAST(FTS.GROUP_C AS BIGINT)) AS GROUP_C,
SUM(CASE WHEN FAT.PERCENTAGE_USED <= '0.10' THEN 1 ELSE 0 END) AS PROJECTS_L10,
SUM(CASE WHEN FAT.PERCENTAGE_USED >= '0.50' THEN 1 ELSE 0 END) AS PROJECTS_G50,
SUM(CASE WHEN FAT.PERCENTAGE_USED >= '1.00' THEN 1 ELSE 0 END) AS PROJECTS_G100,
DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE) AS DAYS_LEFT,
(DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE))/7 AS WEEKS_LEFT,
DAYS(DATE('2013-12-31')) - DAYS(CURRENT DATE) AS DAYS_LEFT_YEAR
FROM FACT_TABLE AS FAT
INNER JOIN GROUPS AS FTS ON FAT.DIM_PROJECT_ID = FTS.DIM_PROJECT_ID
GROUP BY FAT.DIM_BUILDING_ID, FAT.BUILDING_NAME;
不需要ELSE 0
,但有些人喜歡在查詢中看到它。
或者這應該也可以:
COUNT(CASE WHEN FAT.PERCENTAGE_USED >= '0.50' THEN 1 END) AS PROJECTS_G50,
我會做這樣的事情:
select bn.building_name ,
t.*
from ( select fat.building_id ,
sum( case when fat.percentage_used <= 0.10 then 1 else 0 end ) as group_a ,
sum( case when fat.percentage_used > 0.10 and fat.percentage_used < 0.50 then 1 else 0 end ) as group_b ,
sum( case when fat.percentage_used >= 0.50 and fat.percentage_used < 1.00 then 1 else 0 end ) as group_c ,
sum( case when fat.percentage_used >= 1.00 then 1 else 0 end ) as group_d ,
sum( case when fat.percentage_used is null then 1 else 0 end ) as group_e
from fact_table fat
join groups fts on tfs.dim_project_id = fat.dim_project_id
group by fat.building_id
) t
join fact_table bn on bn.building_id = t.building_id
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