[英]oracle query nested select using case
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;
结果:
FLAG_MYTABLE_A
--------------
0
FLAG_MYTABLE_B
--------------
1
我需要构建此查询的帮助,因此可以显示以下结果。
MYTABLENAME MYFLAG
----------- ------
MYTABLE_A 0
MYTABLE_B 1
我在看嵌套选择吗? 有人可以告诉我如何设置吗?
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;
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
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