as the title, my question is, for example, there is a table with five pieces of data in it, respectively * 1 * { "_id" : ObjectId("5b50807f334ca1071be530aa"), "a" : , "a" : 2 } * 2 * { "...
thinking about doing homework. If there is such a check-in system Design according to the paradigm College schedule course schedule (College schedule one to many) teacher schedule Student schedule Teaching schedule (teacher schedule many to many...
Hello, everyone. At present, there is a database query design problem: action table: user_id, action_detail 1 "action_click" 2 "action_drag" user info tablle user_id, full_name, email 1 "User One&q...
there is a system that has no source code and cannot find a developer. Now I want to make a report by myself, but I have encountered a disgusting problem. Consult database SQL SERVER 2008 R2 the simplified table structure is as follows id customer ID...
scenario: users leave comments on certain works, etc. A single table in the database stores these messages, which contains information such as the user s profile picture and nickname. Scheme: user id, is used in the comment table to associate...
the company s product tables currently have 3, and there may be 20 + in the future, and the amount of data varies from tens of thousands to millions, each of which needs to be maintained separately and cannot be merged together. At present, I want to c...
first of all, mongodb is installed normally. It is installed in D: mongodb (folder), and the database is stored in D: mongoData (database folder). When joining the system service, it is added through configuration file parameters (mongodb version 3.6) ...
CREATE OR REPLACE PROCEDURE QD_MYDTJ (BEGINDATE VARCHAR2, ENDDATE VARCHAR2, xz_name VARCHAR2, xz_number VARCHAR2, --BEGININTEVAL VARCHAR2, --ENDINTEVAL VARCHAR2, start1 IN NUMBER, limit1 IN NUMBER, AN_O_RET_CODE ...
can JVM handle deadlocks in the same way as database transactions? If not, then what is the reason? throw a brick to attract jade: the phenomenon of sequential deadlock is described in Java concurrent programming practice, and the philosopher dining...
in development, there are some scenarios where we need to store information for a time period in the database. For example, an event has a start time and an end time, and we can store it in the database with two fields such as startDate and endDate. But...
I have seen all kinds of connection pooling, and some of them will suspend themselves when they are exhausted and will not accept additional connection acquisition requests. When some connection pooling connections are exhausted, additional connection ac...
for example: < table > < thead > < tr > < th > id < th > < th > num < th > < tr > < thead > < tbody > < tr > < td > 1 < td > < td > 1 < td > < tr > < tr > < td > 2 < td > < td > 20 < td > < tr > < tr > < td > 3 < td > < td > 30 < ...
I want to restore a single table, the command written like this mongorestore --username admin --password "pwdmongo" --db poi --collection newPoi newPoi.bson but keep prompting errors connected to: 127.0.0.1 assertion: 18 { ok: 0.0, errmsg: ...
I check in the background that there are multiple indexes of a table in the database I have rebuilt a table. Is there any way to add all the indexes to ...
Project background: the intranet OLAP application, specifically, is a variety of statistical charts for leaders to see. The project concurrency is small, so multiple threads can be used for a single request. The bottleneck is that the statistics of SQL ...
MyIsam only supports table locks. Many places say that deadlocks will not occur in MyIsam. Is that so? If my two transactions query two tables and add write locks at the same time, but the locking order is not the same, will it deadlock? ...
1.golang reported an error 2 when using sqlx s transaction. The code is as follows package main import ( "log" _ "github.com lib pq" PostgreSQL "github.com jmoiron sqlx" "github.com lib pq" ...
:projectDao.js var mongoose = require( mongoose ) const Project = mongoose.model( Project ) exports.createProject = async(data) => { data.m.projectModelId=data.m.projectModel.split( , )[0] data.m.projectModelName=data.m.projectModel.spli...
I am a novice in database. Recently, when using spring-data-jpa, I encountered the problem that I could not design entity classes according to the Emurr model, so I asked a question. Emurr model is shown in the following figure: consider Company a...
the card has been wrong in ERROR all day. Ask the bosses for help. the core error report is shown in the figure: the complete code is here: <?php header( Content-Type:textml;charset=utf-8 ); $username= ; $account=$_POST[ account ]; $p...