为什么数据库要有主从表之分

页面:/news/view-2112121/ | 耗时:0.4267 s | 内存:1.89 MB | 查询:4 | 缓存读取:4 写入:0 | 加载文件:23
select * from tbl_Articles WHERE ArticleID=2112121 LIMIT 0,1
select * from tbl_Articles_data WHERE ArticleID=2112121 LIMIT 0,1
select * from tbl_Articles_sphinx where id=2112121 LIMIT 0,1
SELECT ArticleID,Title FROM tbl_Articles WHERE ArticleID IN(1105785,1080805,1102554,1087337,1081997,1122841,1055758,1128237,1075883,1072673,1071691,1119934,1072681,1067591,1070692,1046866,1072637,1124043,1071843,1093192,1082357,1078380,1090338,1128117,1130158,1112004,1083618,1098545,1131171,1131912) ORDER BY field (ArticleID,1105785,1080805,1102554,1087337,1081997,1122841,1055758,1128237,1075883,1072673,1071691,1119934,1072681,1067591,1070692,1046866,1072637,1124043,1071843,1093192,1082357,1078380,1090338,1128117,1130158,1112004,1083618,1098545,1131171,1131912)