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...
question: use html-webpack-plugin to inject js files into template files. If a.js needs to introduce b.js in head, how should html-webpack-plugin be configured if it needs to be introduced in body? A.js is a global script file. ...
to achieve the 60 seconds countdown after sending CAPTCHA, you can click again, but if you use setData to set the button button to disable, there is an asynchronous problem. When the countdown is 0, the crazy button can send several CAPTCHAs. How to sol...
form class: from flask_wtf import FlaskForm from wtforms import StringField,PasswordField,BooleanField,SubmitField from wtforms.validators import DataRequired,Length class LoginForm(FlaskForm): username = StringField( : ,validators=[DataRequired...
currently in the project, you want to use php s pcntl_fork to create multiple processes (such as 8) to consume redis queue messages in parallel. But running the log found that there were not eight processes generated, but two or three. As shown below: ...
![...] when webpack wants to introduce an external questionnaire, it is found that an error is reported. How to solve this problem? ...