CREATE TABLE [dbo].[TopicKeyword] (
    [Id]      SMALLINT      NOT NULL,
    [Keyword] VARCHAR (100) NOT NULL,
    [Volume]  INT           NOT NULL,
    [PageId]  SMALLINT      NOT NULL,
    CONSTRAINT [PK_TopicKeyword] PRIMARY KEY CLUSTERED ([Id] ASC),
    CONSTRAINT [AK_TopicKeyword_Keyword] UNIQUE NONCLUSTERED ([Keyword] ASC),
    CONSTRAINT [FK_TopicKeyword_PageMeta] FOREIGN KEY ([PageId]) REFERENCES [dbo].[PageMeta] ([Id])
);

GO
CREATE NONCLUSTERED INDEX [IX_TopicKeyword_PageId]
    ON [dbo].[TopicKeyword]([PageId] ASC);

GO
CREATE UNIQUE NONCLUSTERED INDEX [IX_TopicKeyword_Id_PageId]
    ON [dbo].[TopicKeyword]([Id] ASC, [PageId] ASC);

CREATE TABLE [dbo].[TopicContent] (
    [ParentKeywordId] SMALLINT NOT NULL,
    [KeywordId]       SMALLINT NOT NULL,
    CONSTRAINT [PK_TopicContent] PRIMARY KEY CLUSTERED ([ParentKeywordId] ASC, [KeywordId] ASC),
    CONSTRAINT [FK_TopicContent_TopicCluster] FOREIGN KEY ([ParentKeywordId]) REFERENCES [dbo].[TopicCluster] ([KeywordId]),
    CONSTRAINT [FK_TopicContent_TopicKeyword] FOREIGN KEY ([KeywordId]) REFERENCES [dbo].[TopicKeyword] ([Id]),
    CONSTRAINT [CK_TopicContent_ParentKeywordId] CHECK ([ParentKeywordId]<>[KeywordId])
);

GO
CREATE NONCLUSTERED INDEX [IX_TopicContent_KeywordId]
    ON [dbo].[TopicContent]([KeywordId] ASC);

CREATE TABLE [dbo].[TopicCluster] (
    [KeywordId] SMALLINT NOT NULL,
    [PageId]    SMALLINT NOT NULL,
    CONSTRAINT [PK_TopicCluster] PRIMARY KEY CLUSTERED ([KeywordId] ASC),
    CONSTRAINT [AK_TopicCluster_PageId] UNIQUE NONCLUSTERED ([PageId] ASC),
    CONSTRAINT [FK_TopicCluster_TopicKeyword] FOREIGN KEY ([KeywordId]) REFERENCES [dbo].[TopicKeyword] ([Id]),
    CONSTRAINT [FK_TopicCluster_TopicKeyword2] FOREIGN KEY ([KeywordId], [PageId]) REFERENCES [dbo].[TopicKeyword] ([Id], [PageId])
);

GO
CREATE NONCLUSTERED INDEX [IX_TopicCluster_KeywordId_PageId]
    ON [dbo].[TopicCluster]([KeywordId] ASC, [PageId] ASC);