SQLServer 主キーの追加

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USE [DB1]
GO
ALTER TABLE [table1] ADD PRIMARY KEY ([col1], [col2])
GO
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※PRIMARY KEYを設定する列⇒NOT NULLが必要になる
・nullable → not null

alter table [table1] alter column [col1] [nvarchar(20)] not null;

・not null → nullable

alter table [table1] alter column [col1] [nvarchar(20)] null;