A Set is a "collection that contains no duplicate elements."
Set是不包含重复元素的集合。
Retention and reuse also mean that no duplicate work needs to be performed each time a newer version of the application is released.
保留和重用还意味着每当发行应用程序的新版本时，不需要做重复的工作。
A collection that contains no duplicate elements.
不包含重复元素的集合。
A primary key is a constraint that assures that each table contains no duplicate rows.
主键是确保每个表都不包含重复行的约束。
Create a unique constraint to ensure no duplicate values are entered in specific columns that do not participate in a primary key.
创建唯一约束可确保在不参与主键的特定列中不输入重复值。
Create a unique constraint to ensure no duplicate values are entered in specific columns that do not participate in a primary key.
创建唯一约束可确保在不参与主键的特定列中不输入重复值。
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