优化sql:select * from tab_iptv_info t where t.USERCODE,t.STBCODE, t.STBMAC in (select USERCODE,STBCODE, STBMAC from tab_iptv_info_bak);

可以优化成以下两种方式：

1. 使用INNER JOIN代替IN子查询：

SELECT t.*
FROM tab_iptv_info t
INNER JOIN tab_iptv_info_bak b ON t.USERCODE = b.USERCODE AND t.STBCODE = b.STBCODE AND t.STBMAC = b.STBMAC;

2. 使用EXISTS代替IN子查询：

SELECT t.*
FROM tab_iptv_info t
WHERE EXISTS (
    SELECT 1 
    FROM tab_iptv_info_bak b 
    WHERE t.USERCODE = b.USERCODE AND t.STBCODE = b.STBCODE AND t.STBMAC = b.STBMAC
);

这两种优化方式都能提高查询效率，具体哪种更优取决于数据量和索引情况。