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关系代数的SQL查询_Sql_Relational Algebra - Fatal编程技术网
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关系代数的SQL查询

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关系代数的SQL查询,sql,relational-algebra,Sql,Relational Algebra,我有一个疑问： SELECT DISTINCT a.aanbieding_id FROM aankoop as a WHERE 2 <= (SELECT COUNT(*) FROM aankoop WHERE a.aanbieding_id = aankoop.aanbieding_id) ORDER BY aanbieding_id 但我很确定这是完全错误的，有人能帮我吗 πid(F(count)(aanbieding_id)>=2(Aankoop))

我有一个疑问：

SELECT DISTINCT a.aanbieding_id
FROM aankoop as a 
WHERE 2 <= (SELECT COUNT(*) FROM aankoop WHERE a.aanbieding_id = aankoop.aanbieding_id) 
ORDER BY aanbieding_id
但我很确定这是完全错误的，有人能帮我吗

πid(F(count)(aanbieding_id)>=2(Aankoop))