Menggunakan beberapa kueri bersarang di Oracle DBMS

Permintaan Anda:

SELECT Email, Phonenumber
FROM EMPLOYEE
WHERE COUNT(
ID = (SELECT ID_Num
FROM SCHEDULE
WHERE Start_Time <= 12:07 AND End_Time >= 12:07)
AND Shopn = (SELECT Shopname
FROM SHOP
WHERE Shoptype = ‘market’) ) > 2

Masalah :

1. Sepertinya Anda mencoba memilih id menggunakan operator "=" yang akan gagal jika beberapa entri dikembalikan oleh kueri dalam.
2. Anda tidak dapat menambahkan operator agregat di klausa where.

Kemungkinan Jawaban:

select Email, Phonenumber
FROM EMPLOYEE
WHERE ID in (SELECT ID_Num
FROM SCHEDULE
WHERE Start_Time <= '12:07' AND End_Time >= '12:07')
AND Shopn in (SELECT Shopname
FROM SHOP
WHERE Shoptype = 'market')
and (  
select count(distinct id)
FROM EMPLOYEE
WHERE ID in (SELECT ID_Num
FROM SCHEDULE
WHERE Start_Time <= '12:07' AND End_Time >= '12:07')
AND Shopn in (SELECT Shopname
FROM SHOP
WHERE Shoptype = 'market')) > 2;