Sql_Server中怎么判断表中某列是否存在

/*判断表AA中是否存在AA_ID这一列，如果不存在，则新增*/IF NOT EXISTS (SELECT 1  FROM syscolumns INNER JOIN sysobjects ON sysobjects.id = syscolumns.id 		WHERE syscolumns.name = 'AA_ID' AND sysobjects.name = 'AA')ALTER TABLE AA ADD AA_ID VARCHAR(30) NULL   GO