Oracle 4种等价SQL

SQL查询技巧：复杂数据集过滤与匹配

最新推荐文章于 2022-02-16 17:30:22 发布

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本文深入探讨了SQL查询中如何通过多级筛选与数据匹配，实现复杂数据集的有效过滤与精确检索。从基本的COUNT(1)查询出发，逐步引入GROUP BY、JOIN、DISTINCT等关键操作，展示如何高效地处理并分析大型数据库中的信息。重点涵盖了通过子查询、NOT EXISTS等逻辑条件构建高级查询策略，确保数据准确性和效率。


SELECT COUNT (1) FROM (SELECT k001 FROM ( SELECT k001 FROM kbib GROUP BY k001) k
WHERE NOT EXISTS ( SELECT 1 FROM ( SELECT k003 FROM calb GROUP BY k003) c WHERE k.k001 = c.k003))

SELECT COUNT (1) FROM (SELECT k001 FROM ( SELECT k001 FROM kbib GROUP BY k001) k
WHERE NOT EXISTS ( SELECT k003 FROM calb WHERE k.k001 = k003 GROUP BY k003))

SELECT count (1) FROM (SELECT * FROM ( SELECT k001 FROM kbib GROUP BY k001) k
WHERE k.k001 NOT IN ( SELECT k003 FROM calb c WHERE k.k001 = c.k003 GROUP BY k003))


SELECT count (1) FROM (SELECT * FROM ( SELECT DISTINCT k001 FROM kbib) k
WHERE k.k001 NOT IN ( SELECT DISTINCT k003 FROM calb c WHERE k.k001 = k003))