CREATE TABLE dbo.ci_sessions (
    session_id varchar(40) DEFAULT '0' NOT NULL,
    ip_address varchar(16) DEFAULT '0' NOT NULL,
    user_agent varchar(120) NOT NULL,
    last_activity int DEFAULT 0 NOT NULL,
    user_data ntext NOT NULL,
    PRIMARY KEY (session_id)
)
GO

-- Simalate MySQL 'UNSIGNED' field option

ALTER TABLE dbo.ci_sessions ADD CONSTRAINT last_activity_unsigned
  CHECK (last_activity >= 0)
GO

CREATE INDEX last_activity_idx
  ON dbo.ci_sessions (last_activity)