oracle oracle查询嵌套选择用例
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时间：2020-09-19 00:44:09 来源:igfitidea点击:
oracle query nested select using case
提问by cjd143SD
I have (2) case statements:
我有（2）个案例陈述：
SELECT CASE WHEN EXISTS
( SELECT *
FROM MYTABLE_A
WHERE timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
)
THEN 0
ELSE 1
END AS FLAG_MYTABLE_A
from DUAL;
SELECT CASE WHEN EXISTS
( SELECT *, timestamp
FROM MYTABLE_B
WHERE
timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
) )
THEN 0
ELSE 1
END AS FLAG_MYTABLE_B
from DUAL;
RESULTS:
结果：
FLAG_MYTABLE_A
--------------
0
FLAG_MYTABLE_B
--------------
1
I need help constructing this query so I can get the following results displayed.
我需要帮助构建此查询，以便显示以下结果。
MYTABLENAME MYFLAG
----------- ------
MYTABLE_A 0
MYTABLE_B 1
Am I looking at a nested select? Can someone show me how to set this up?
我在看嵌套选择吗？有人可以告诉我如何设置吗？
回答by Lamak
You can use UNION ALL:
您可以使用UNION ALL：
SELECT 'MYTABLE_A' AS MYTABLENAME, CASE WHEN EXISTS
( SELECT *
FROM MYTABLE_A
WHERE timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
)
THEN 0
ELSE 1
END AS FLAG_MYTABLE_A
from DUAL
UNION ALL
SELECT 'MYTABLE_B' AS MYTABLENAME, CASE WHEN EXISTS
( SELECT *, timestamp
FROM MYTABLE_B
WHERE
timestamp = to_char(sysdate-1, 'yyyymmdd') || '0000'
) )
THEN 0
ELSE 1
END AS FLAG_MYTABLE_B
from DUAL;
回答by Pavel Veller
You can do something like:
您可以执行以下操作：
SELECT "MYTABLE_A", CASE ... END AS "MYFLAG" FROM DUAL
UNION
SELECT "MYTABLE_B", CASE ... END AS "MYFLAG" FROM DUAL
