has such a logic, a piece of data, if there is in the database, then update, if it does not exist, then insert. But now there are ten thousand. So how to accomplish the task efficiently? ...
take MySQL as an example, what is the difference (principle and efficiency) between in and exists and between not in and not exists? What about using indexes? Say that not in and < > will not use indexes, won t you? ...
The index is a data structure in which the leaf node of the b + tree holds pointers to the actual rows. what about clustered indexes? what does InnoDB s clustered index mean by storing B+Tree indexes and data rows in the same structure? Does mean that...
EXPLAIN SELECT s.id, s.name, s.price, s.unit, s.qty, s.remark, s.image, s.cuft, s.volume, s.status, s.vender_id AS venderId, s.booth_id AS boothId, s.booth_no AS boothNo, s.show_booth_no AS showBoothNo, s.name_en AS nameEn, ...
such as the title. see that MySQL generates a tree for the primary key, and the leaf node holds the row data corresponding to the primary key. The secondary index leaf node holds the value of the primary key. excuse me: does the leaf node of th...
nginx is a mirror image on docker. The blog.conf configuration under conf.d is as follows 8080 ...
uses django+uwsgi+nginx to develop a background management system, which is not used by many people, and there is no performance problem. But there has always been a problem, that is, occasionally encountered, with a sudden login user becomes another. W...
looked at the table component of the element-ui framework: when there are many fields, fill the width tableelement ...
body { font-size: 20px; line-height: 2; } .em { font-size: 2em; background: -sharpccc; } how much should the line-height above be in the end? I m not sure: .em inherits the line-height property of body, does it inherit the value of 2...
when deleting data is selected, the selected data id forms an array, and then deletes the data from the first layer of all data arrays, and if the data has this data in the children,children, delete the data from the first layer data = [{] flg: &q...