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?
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for example, the isolation level of transaction An is repeatable read my understanding is that a read sql statement of transaction An is the same as the result repeated many times, regardless of whether or not other transactions have changed the data ...
in sql server database, an insert trigger is set for a table, and a new view is created in the trigger. How to design and write statements? Thank you ...
there are 200000 data in the data, and each data has a typical list of words of 5000 length [{aVl1}, {bju 2},.], and typical dictionaries of 5000 length {{aRom 1}, {bjr 2},.}, use pyMongo to find100 data, the traversal of cursor is particularly slow, is...
as shown in the figure below, does SQLAlchemy have a simple way to directly declare that the specified field is not mapped serialized? for example, does java s Hibernate framework have such a function? (although there are other "indirect " solut...
as shown in the figure, a simple add and query operation takes up to 1 second [environment: windows + python3 + django2]. (the amount of data in PS: is not much, and todo_list has only 2 rows of data, which is still so slow.) def get(request): -...
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designing a complete project includes not only the front-end project design, but also the need to build local servers and databases. As a front-end developer, what kind of database should you choose? There are a lot of people around who are using mongodb...
how do you design database fields like youtube pages that show whether you have pressed like or dislike? And go to the database to judge when the user arrives at the page? whether the design idea is like this Post table id picroute likeusers dislik...
2018-04-10T08:26:03.830775Z 0 [Note] usr sbin mysqld (mysqld 5.7.20) starting as process 9836 ... 2018-04-10T08:26:03.923709Z 0 [Note] InnoDB: PUNCH HOLE support available 2018-04-10T08:26:03.923741Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic b...
Table T_USER T_ROLE : the following is the table creation and data script drop table if exists T_USER; CREATE TABLE T_USER( USER_ID INT, USER_NAME VARCHAR(25) ); INSERT INTO T_USER VALUES(1, USER_A ); INSERT INTO T_USER VALUES(2, USER_B )...
what databases are used by app with a very large amount of data, such as facebook, Weibo, Jinri Toutiao and so on? how to ensure access speed? ...
background: I want to add tagging capabilities for our products. A product can have multiple tags, and each tag can be used by multiple products, which is the so-called many-to-many relationship. specific: We have 10 million products Product, admi...
mongoose What is the reason for ? ...
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 ....
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...
if the data to be saved contains "`, how can it be inserted into the database? A rookie, please give me some advice. ...
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...
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? ...
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. ...
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...