如何判断两条线段是否垂直

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select * from tbl_Articles WHERE ArticleID=1604020 LIMIT 0,1
select * from tbl_Articles_data WHERE ArticleID=1604020 LIMIT 0,1
select * from tbl_Articles_sphinx where id=1604020 LIMIT 0,1
SELECT ArticleID,Title FROM tbl_Articles WHERE ArticleID IN(915261,468335,1081221,138186,180703,809122,753068,1749515,554458,667019,319818,1361373,1900592,891338,1126579,785932,1125060,1334142,889302,1779583,1348258,1319873,778229,938253,1421091,1055405,1315255,1127381,2673893,203330) ORDER BY field (ArticleID,915261,468335,1081221,138186,180703,809122,753068,1749515,554458,667019,319818,1361373,1900592,891338,1126579,785932,1125060,1334142,889302,1779583,1348258,1319873,778229,938253,1421091,1055405,1315255,1127381,2673893,203330)