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see View all indexes in the database db.system.indexes.find () db.system.indexes.find () on the Internet. Why is it so after I type it ...
1. How to decompose (A, B)-> E, (C, D)-> E, A-> C, C-> An into BCNF,? 2, U = (Agraine Brecinct C pyrrhene E) F = {B-> Greco ce-> Breco C-> Areco B-> Dle le C-> D}. Decompose into BCNF? 3. The BCNF decomposition that I understand at present is to fin...
recently, I have been learning distributed architecture. I have basically figured it out. What about the database? the mysql, I ve been using take mysql as an example for example, I now have two databases of server B. According to the load balancer,...
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 mobile version can t upload the picture, go back to make it up tonight) General uid. If the figure above is a string of fixed-length numbers, how is it generated? When storing uid in a database, doesn t it usually start at 1 and then grow itsel...
what do you mean by sub-database and sub-table partitioning of the database? ...
after reading this article (introducing schema in the database) https: www.biaodianfu.com da., it is mentioned that the schema in MySQL is the same as the library. Is this correct? Thank you ....
Database oralce query data based on the following parameters how to query, do you have any ideas? ...
seniors, I have a problem that I can t solve. I hope you can take the time to answer it. I want to print the data from the database through vue-markdown, but after going through it with v-for, I get undefined. Also used v-text instead of {{}} to outp...
for example, go connection mysql, https: github.com jmoiron sqlx is a client that implements official database sql, and an additional driver: https: github.com go-sql-dri. is required to use it. but this is not the case when I connect to mongodb. ...
there is a new requirement that needs to add a field X to the table TABlE_A. Suppose X has values of 0 and 1, but for historical data, the value of this field is NULL,. What do you prefer to do at this time? data revision. Brush over the historical d...
first of all, I found a lot of database design on Baidu, it can be said that there are different opinions! I see an intermediate table is designed like this, commodity ID sku attributes, unit price inventory, see that the intermediate attributes store js...
how do facebook, Weibo comments and comment responses and comment likes be stored? It feels like it takes a lot of effort to use a relational database. ...
for example, the comment table is divided into 100tables and divided according to the userid hash algorithm, so the background management should display the comment list, but cannot jointly query 100tables. How do you do this? ...
I have a company employee mailing list and a new employee mailing list. I need to open an email for new employees. I ve been using excel manually. I want to try to use access to automatically achieve . I need to query the duplicate name and add the nu...
if the data to be saved contains "`, how can it be inserted into the database? A rookie, please give me some advice. ...
because InfluxDB clusters are charged. Now you are ready to use message queuing to solve the normal data Synchronize of the InfluxDB database cluster. But if a database server goes down, and then restart and start, how to recover the data and turn the da...
prepare to develop book reading class app, backend to choose which database can better store book content. In the past, relational databases were used. Experienced people can guide them ....
mongoose What is the reason for ? ...
problem description use malloc to apply for space in a function in a C language project. Finally, the function returns the value saved in this space, that is, there is no space requested by free in the function, so do you need free outside the functio...
1 how to achieve automatic rotation to ensure reliability 2 how to enable client An of server1 to push information to client B of server2 in a websocket cluster 2 how to make client An of server1 push information to client B of server2? ...
cnpm image-webpack-loader gifsicle build:webpack g I installed a libpng library on the server, but two more dependencies were not installed. ...
I use fiddle to grab the package to see if js is loaded. It was observed that other browsers (QQ Browser, the system s built-in browser and the safari,ios version of QQ) were normal, and the UC browser on the IOS system could not be loaded alive or dead...
for example, the following configuration block. I have N PHP sites, and they all have the same configuration items except server_name and root. Is there any way to reuse the same configuration? by the way, is there a security risk to my next configura...