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...
problem description as the title error message this.getCurrentPage is not a function;at App setPageUserInfo function TypeError: this.getCurrentPage is not a function related codes Please paste the code text below (do not replace the code wit...
vue-cli introduce element using cdn in index.html <link rel="stylesheet" href="https: unpkg.com element-ui@2.3.7 lib theme-chalk index.css"> <script src="https: cdn.bootcss.com vue 2.5.2 vue.min.js">< ...
$arr = [ fileurl => , uploadtype => 20 , fileid => *0*eO7SsKNr2PQTlqxi3TVgYeimS4KBbxDQPgKSswBv1YsngmLB4FKzVGwZhY+MTDk bzK58bxtY59daaLuC5HNobhmZHMOtkBvNNDiQXq2c0qMtn5PWxsxYFuv40ZG3N9s9qe2X7MWN 38WIHiB771JpaaHkrdtvCzNp V...
the vue project uses "vue-awesome-swiper ": "^ 2.5.4 " to realize the rotation error report. steps are as follows: 1, install 2, introduce component reference import { swiper, swiperSlide } from vue-awesome-swiper export default { ...
as shown in the figure, I want to add a line of text and pictures to the multi-line text box, but in Mini Program, textarea seems to be the highest level by default. Setting z-index does not work, and textarea will always overwrite this line of text ...