SELECT A.Id, AMerge.FeildA, AMerge.FeildB, AMerge.FeildC, BMerge.FeildD, BMerge.FeildE, BMerge.FeildF,
FROM
(SELECT Id, FieldA, FieldB, FieldC from A1
UNION ALL
SELECT Id, FieldA, FieldB, FieldC from A2
) AS A
INNER JOIN
(
SELECT Id, FieldD, FieldE, FieldF FROM B1
UNION ALL
SELECT Id, FieldD, FieldE, FieldF FROM B2
) AS B
ON A.Id = B.Id
其中,A = 8102869,n = B = 17935860,导致表大小n = 17935860。MSSQL性能 - 连接上的大数n
如何重构此查询以提高效率,或者我可以在表或数据库上执行哪些流程以提高上述查询的性能?
你有什么指标,你有什么数据? – Jester
如果这是MySQL的请用'EXPLAIN SELECT ...'的输出更新你的问题。 – Xint0