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(_) ; | |
(%) ; |
, , . | |
IS NULL. . , . . : . : |
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.
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FROM R
UNION
SELECT S.b2, S.b1
FROM S
, , :
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SELECT , AS /
FROM
UNION
SELECT _, AS /
FROM
R S , , .
(SELECT R.a1, R.a2
FROM R)
INTERSECT
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FROM R,S
WHERE R.a1=S.b1 AND R.a2=S.b2
SELECT R.a1, R.a2
FROM R
WHERE R.a1 IN
(SELECT S.b1 FROM S
WHERE S.b1=R.a1) AND R.a2 IN
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FROM S
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, ,
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FROM )
INTERSECT
(SELECT _
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FROM R
WHERE NOT EXISTS
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FROM S
WHERE S.b1=R.a2 AND S.b2=R.a1)
(SELECT R.a1, R.a2
FROM R)
EXCEPT
(SELECT S.b1,S.b2
FROM S)
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SQL . , ( WHERE HAVING), , . EXISTS, , .
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FROM R1 AS A, R1 AS B
FROM R1 A, R1 B;
SELECT R1.
: