必要不充分条件是什么意思

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select * from tbl_Articles WHERE ArticleID=3447880 LIMIT 0,1
select * from tbl_Articles_data WHERE ArticleID=3447880 LIMIT 0,1
select * from tbl_Articles_sphinx where id=3447880 LIMIT 0,1
SELECT ArticleID,Title FROM tbl_Articles WHERE ArticleID IN(403321,419117,1105379,699484,2985999,1115751,417866,1120739,412388,1195725,1122787,2618788,1087769,725476,1117333,3392498,401765,80171,1102516,410190,87081,1847464,1092280,3394927,1082483,1093358,922000,1099323,368727,451584) ORDER BY field (ArticleID,403321,419117,1105379,699484,2985999,1115751,417866,1120739,412388,1195725,1122787,2618788,1087769,725476,1117333,3392498,401765,80171,1102516,410190,87081,1847464,1092280,3394927,1082483,1093358,922000,1099323,368727,451584)