在SQL Server中，可以使用以下方法来对字段进行去重：
SELECT DISTINCT column_name
FROM table_name;
SELECT column_name
FROM table_name
GROUP BY column_name;
SELECT column_name
FROM (
SELECT column_name, ROW_NUMBER() OVER (PARTITION BY column_name ORDER BY column_name) as row_num
FROM table_name
) t
WHERE t.row_num = 1;
