背景 在数据库中NULL值是指UNKNOWN的值,不存储任何值,在排序时,它排在有值的行前面还是后面通过语法来指定. 例如 -- 表示null排在有值行的前面 select * from tbl order by id nulls first; -- 表示null排在有值行的后面 select * from tbl order by id nulls last; 同时对于有值行,可以指定顺序排还是倒序排. -- 表示按ID列顺序排 select * from tbl order by id [a
mysql默认的排序: https://forums.mysql.com/read.php?21,239471,239688#msg-239688 Do not depend on order when ORDER BY is missing. Always specify ORDER BY if you want a particular order -- in some situations the engine can eliminate the ORDER BY because of h
C. Table Compression Little Petya is now fond of data compression algorithms. He has already studied gz, bz, zip algorithms and many others. Inspired by the new knowledge, Petya is now developing the new compression algorithm which he wants to name d
表格默认选中行,在回调里写入 done: function (res, curr, count) { tableData = res.data; $("[data-field='id']").css('display', 'none'); var data = res.data; var num = 0; for (var i = 0; i < data.length; i++) { if (ExamStudentArray.indexOf(data[i].id) != -1)