Programmer Think

Thank you for your little love (attention + praise + look again). Your affirmation of the blogger will urge the blogger to continuously output more high-quality practical content!!! 1. Preface - structure of this paper Big data sheep said Using data to improve the probability of good things~ 32 original content official account Thi ...

1. Why master slave copy In a system with complex business, there is a scenario in which an sql statement needs to lock the table, resulting in the temporary inability to use the read service, which will greatly affect the running business. Use master-slave replication, and let the master database be responsible for writing and the slave datab ...

sql injection is When the user enters some sql statements that are not the user name or password These statements are not filtered After execution, the injector obtains the information of the database through echo and other methods Water has been used for several days for visual studio 2022 and windows 11, so this article is a little ...

When using Linq to sql in C#, IQueryable and IEnumerable are often confused. This article briefly analyzes the differences and usage scenarios between them. preface Whether Linq to object, Linq to sql or Linq to Entity, IQueryable and IEnumerable are delayed execution. The only difference between them lies in the parameter types of extension ...

Python learning log Home page of RBHGO Welcome to pay attention Warm tip: creation is not easy. If reprinted, indicate the source. Thank you for your cooperation~ catalogue Python learning log Lesson 17 - Python database programming DCL (data control language) DCL - > grant or recall user permission - > grant / revoke In ...

Create relevant views according to the data dictionary to facilitate query create schema dba; create view dba.ro_conflicts as select datname,pg_stat_get_db_conflict_all(oid) conflict_all,pg_stat_get_db_conflict_bufferpin(oid) conflict_bufferpin,pg_stat_get_db_conflict_lock(oid) conflict_lock,pg_stat_get_db_conflict_snapshot(oid) conflict_ ...

Access Remote Sources with SAP HANA Database Explorer Remote sources are connections to other databases. Virtual tables use remote sources to create local tables that point to data stored in another database. Federated queries use virtual and non virtual tables. To illustrate these concepts, a table will be created in the remote database cont ...

Welcome to the MySQL technical articles shared by the great SQL community. If you have any questions or want to learn, you can leave a message in the comment area below. After seeing it, you will answer itThe original content of GreatSQL community cannot be used without authorization. Please contact Xiaobian and indicate the source for reprint. ...

SQL07 set calculation Relational Division Define table R and table S as follows R XYX1Y1X2Y2X2Y3X2Y3X3Y1X3Y2 S YFY1F1Y2F2 For relationships (tables) with the same attributes, R and S relationship division is mainly divided into the following steps: 1. Find the same attribute y. Project y in relation R, that is, take out the value of Y ​ ...

join query Meaning: it is also called multi table query. When the query fields come from multiple tables, the join query will be used Cartesian product phenomenon: Table 1 has m Row, table 2 has n Line, result=m*n that 's ok Cause: there is no valid connection condition How to avoid: adding valid connection conditions As follows: #Without ...