UNIQUE NULLS NOT DISTINCT
已记录的来源状态与原始语言说明；缺少版本证据时明确标为未知。
来源快照记录 PostgreSQL 8.1–18 的变化节点；历史矩阵独立记录 7.4–18 的状态。两者均未记录 PostgreSQL 19 或 20 的支持状态，较新版本明确保留为未知。这些来源声明与运行测量相互独立。
索引和约束
说明
默认情况下 NULL 彼此不同；在唯一索引或唯一约束上指定 NULLS NOT DISTINCT 后，NULL 会被视为不再互异。
所选版本: PostgreSQL 18
支持
比较版本
原始文档链接
已记录旧标识: 392
完整来源事实与出处
yaml · center · 1dd22bf9a7f3ec325b894e2836fda535a25529f246a94dd41d6abbfe9997f7fd
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