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已关闭8年。
我的SQL技能非常有限，并且由于我最近发现自己经常与DB(Oracle)一起工作，所以我希望超越基本的select语句。
我想编写查询来执行诸如从多个表中获取数据，求和数量，比较日期，分组，过滤器等操作。
您可以推荐哪些站点来将SQL报告技能提高到更高的水平？