Unverified50% confidenceFactExact time
在PostgreSQL中,SELECT NULL = NULL 返回NULL而不是TRUE
1
Sources
50%
Confidence
Long-term
Relevance
9/12/2026
First Seen
Sources
Related Entities
Related Claims
UnverifiedPostgreSQL默认将NULL视为最大值,升序排序中排在末尾,降序中排在开头74% similarUnverifiedPostgreSQL的聚合函数会忽略NULL值:COUNT(*)统计所有行,COUNT(val)、SUM、AVG忽略NULL值73% similarUnverified在SQL的三值逻辑中,任何涉及NULL的比较运算结果都是UNKNOWN,而不是TRUE或FALSE69% similarUnverified如果NOT IN子查询的结果中包含任何NULL,整个查询会返回空集,因此推荐用NOT EXISTS替代68% similarUnverifiedMySQL和PostgreSQL在无法完成类型转换时会抛出错误,而SQLite默认策略是永不失败63% similar
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