FOREIGN KEY: contains no primary or candidate keys - sql-server

Question

In SQL Server , I got this error ->
SQL71516 :: The referenced table '[dbo].[PostsTags]' contains no primary or candidate keys that match the referencing column list in the foreign key. If the referenced column
is a computed column, it should be persisted.
I don't understand why dint works foreign key, without them table created without problems, but I need a relationship between tables, in this location.I looked at other similar questions, but the answers were not found.
CREATE TABLE [dbo].[PostsTags] (
[PostId] INT NOT NULL,
[TegId] INT NOT NULL,
CONSTRAINT [PK_PostsTags] PRIMARY KEY CLUSTERED ([PostId] ASC, [TegId] ASC)
);
CREATE TABLE [dbo].[Comments] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[PostId] INT NOT NULL,
[DateTime] DATETIME NOT NULL,
[Name] NVARCHAR (64) NOT NULL,
[Body] NVARCHAR (MAX) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
CREATE TABLE [dbo].[Tags] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[Name] NVARCHAR (64) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC),
CONSTRAINT [FK_Tags_PostsTags] FOREIGN KEY ([Id]) REFERENCES [PostsTags]([TegId]) ON DELETE CASCADE
);
CREATE TABLE [dbo].[Posts] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[Title] NVARCHAR (128) NOT NULL,
[DateTime] DATETIME NOT NULL,
[Body] NVARCHAR (MAX) NOT NULL,
[Avtor] NVARCHAR (64) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC),
CONSTRAINT [Post_Tag] FOREIGN KEY ([Id]) REFERENCES [PostsTags]([PostId]) ON DELETE CASCADE,
CONSTRAINT [Post_Comment] FOREIGN KEY ([Id]) REFERENCES [Comments]([PostId]) ON DELETE CASCADE,
);
Sorry for bad English.

Answer 1

What you want is this, I'm sure:
CREATE TABLE [dbo].[Tags] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[Name] NVARCHAR (64) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
CREATE TABLE [dbo].[Posts] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[Title] NVARCHAR (128) NOT NULL,
[DateTime] DATETIME NOT NULL,
[Body] NVARCHAR (MAX) NOT NULL,
[Avtor] NVARCHAR (64) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
CREATE TABLE [dbo].[PostsTags] (
[PostId] INT NOT NULL,
[TagId] INT NOT NULL,
CONSTRAINT [PK_PostsTags] PRIMARY KEY CLUSTERED
([PostId] ASC, [TagId] ASC),
CONSTRAINT [FK_PostsTags_Tags] FOREIGN KEY ([TagId])
REFERENCES [Tags]([Id]) ON DELETE CASCADE,
CONSTRAINT [FK_PostTags_Posts] FOREIGN KEY ([PostId])
REFERENCES [Posts]([Id]) ON DELETE CASCADE
);
CREATE TABLE [dbo].[Comments] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[PostId] INT NOT NULL,
[DateTime] DATETIME NOT NULL,
[Name] NVARCHAR (64) NOT NULL,
[Body] NVARCHAR (MAX) NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC),
CONSTRAINT [FK_Comments_Posts] FOREIGN KEY ([PostId])
REFERENCES [Posts](Id) ON DELETE CASCADE
);
That is - you can freely insert into Tags or Posts without consideration of any other tables or data within them. Once there's a row in Posts, you can start adding rows to Comments, provided that the PostId column contains a value that already exists in the Posts table's Id column (Comments references Posts)
Further, once there are rows in both Posts and Tags, only then can you insert rows into PostTags, with again constraints on what values are valid in that table being based on current rows in Posts and Tags.
Finally, I've left your CASCADE options set as in your original. If someone deletes a row from Posts then all rows in Comments that relate to that post are deleted. Similarly, any rows in PostsTags that relate to the post are deleted. If someone deletes a row from Tags then all rows in PostsTags that references that tag are removed.