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...
there are array objects. You want to render by column. One column displays 23 rows, and the first column is greater than 23. Start rendering the second column. The data format is as follows: { "case1": [ { "name&qu...
1. Company development project online test, click on a page, first show the web page can not be displayed, and then jump to the target page, about 1.5 seconds test server used nginx, Baidu related problems, did not find an effective way, has appeared f...
what plug-in caused this? ...
is my dist file correct? I used npm run build to generate the files in the dist directory: there are many .chunk.js files, dozens of them. Is that how you generate them? I want to pack up and publish it on the Internet. Do I have to copy all t...
1. Doing exercises on leetcode, the fifth question, using the central enumeration method. 2. Refer to this blog post: https: blog.csdn.net asd1369.3. The second method used, other code can understand, I directly posted the question code: x= ...