[英]Case expression from another case expression
我有 SQL 代碼示例,它返回周數
,CASE WHEN dateadd(MONTH, datediff (MONTH,AgentStart, getdate()), AgentStart) > getdate()
THEN datediff(MONTH, AgentStart, getdate()) - 1
ELSE datediff(MONTH, AgentStart, getdate())
END as 'Month'
我不知道現在如何添加一個新列,它將給我這個結果(來自同一個表):
,CASE WHEN **MONTH FROM CASE STATEMENT ABOVE** BETWEEN 0 AND 3 THEN 'Youngest'
WHEN **MONTH FROM CASE STATEMENT ABOVE** BETWEEN 4 AND 5 THEN 'Young'
WHEN **MONTH FROM CASE STATEMENT ABOVE** BETWEEN 6 AND 11 THEN 'Medium'
ELSE 'Old'
END AS "Status"
您可以使用子查詢:
SELECT `month`,
CASE WHEN `month` BETWEEN 0 AND 3 THEN 'Youngest'
WHEN `month` BETWEEN 4 AND 5 THEN 'Young'
WHEN `month` BETWEEN 6 AND 11 THEN 'Medium'
ELSE 'Old'
END AS Status
FROM (SELECT CASE
WHEN dateadd(MONTH, datediff (MONTH,AgentStart, getdate()), AgentStart) > getdate()
THEN datediff(MONTH, AgentStart, getdate()) - 1
ELSE datediff(MONTH, AgentStart, getdate())
END as `Month`
FROM mytable) t
您可以編寫一個內聯視圖來完成此操作
例如:
select case WHEN x.month_value BETWEEN 0 AND 3 THEN 'Youngest'
WHEN x.month_value BETWEEN 4 AND 5 THEN 'Young'
WHEN x.month_value BETWEEN 6 AND 11 THEN 'Medium'
ELSE 'Old'
END AS "Status"
,--rest of the columns from the inner query...
from (
select CASE
WHEN dateadd(MONTH, datediff (MONTH,AgentStart, getdate()), AgentStart) > getdate()
THEN datediff(MONTH, AgentStart, getdate()) - 1
ELSE datediff(MONTH, AgentStart, getdate())
END as month_value --naming it as month_value
from <table>
)x
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