CREATE TABLE [dbo].[ActivePair] (
    [ExchangeId] INT           NOT NULL,
    [Base] NVARCHAR (50) NOT NULL,
    [LastDate]   DATETIME      NULL,
    [NonBase] NVARCHAR(50) NOT NULL, 
    [Id] INT NOT NULL IDENTITY, 
    CONSTRAINT [PK_ActivePair] PRIMARY KEY CLUSTERED ([Id])
);