本文详细解析了使用SQL进行表联合查询的方法，包括通过LEFT JOIN和RIGHT JOIN实现的数据整合技巧。通过对三个表a、b、c的操作演示了如何获取不重复记录，并利用UNION ALL进行结果合并。
a表(a,b,c)
b表(a,b,c)
c表(a,b,c)
SELECT DISTINCT a, b, c
FROM (SELECT A.A,a.b,a.c FROM a LEFT JOIN b ON (a.a=b.a))
UNION ALL (SELECT B.A,b.b,b.c FROM a right JOIN b ON (a.a=b.a))
UNION ALL (SELECT C.A,c.b,c.c FROM A RIGHT JOIN C ON (A.A=C.A));
b表(a,b,c)
c表(a,b,c)
SELECT DISTINCT a, b, c
FROM (SELECT A.A,a.b,a.c FROM a LEFT JOIN b ON (a.a=b.a))
UNION ALL (SELECT B.A,b.b,b.c FROM a right JOIN b ON (a.a=b.a))
UNION ALL (SELECT C.A,c.b,c.c FROM A RIGHT JOIN C ON (A.A=C.A));
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