Recently, when I was reading some books on mysql, a year flashed through my mind, B+ tree, HERE I know, B tree, I also roughly understand, then he two are, oh, ha ha ha, forgot, so sometimes it is necessary to summarize a wave of writing tree
When you open a database client, connect to the database, enter a SQL statement, click execute, and output the result. What happens in the process of execution? The following figure shows the schematic diagram of the interaction between the client and MySQL. Trajectory of a query statement The trajectory of a query statement is
Recently, xiaobian hands a bunch of projects, it is very busy, a bunch of batch operations every day, update, import, add, delete, the company uses Mybatis-Plus operation SQL, used Mybatis-Plus partners must know that he has a lot of API for us to use
A dusty man in a plaid shirt walked towards him, holding a MacBook Pro in his hand, looking at the sparse hair, and the calm eyes. My heart a quiver, I go, this is the architect, the architect to face my technical side, my heart suddenly not calm, the surface is very stable in fact a batch of panic. Sure enough, he had my resume in his hand, took a quick look at it, and then looked at it out of the corner of his eye...
Context During actual development, you often need to query the node tree and obtain the list of child nodes based on the specified node. The following describes how to obtain the node tree in case of emergency. The application scenario can be applied to data structures with hierarchical relationships, such as system departments, organizations, commodity categories, and city relationships. The design,
If our business is at a very early stage and the concurrency level is low, we can go years without having a deadlock problem. If our business is at a very high concurrency level, then the occasional deadlock problem will cause us a lot of headaches. However, when the deadlock problem occurs, the first reaction of many inexperienced students is to become an ostrich: this thing is very profound, I can't understand it, just leave it to fate...
== Summary: == If you want to query only NULL columns, use is NULL; if you want to query only NULL columns, use = "". Everyone's support is what keeps me going. Don't forget to follow me at ? and ?!
Many of you know that the size of the sort_buffer in MySQL affects the performance of data sorting. However, you know there is another unknown factor that affects sorting performance. What is it? Today I'm going to dive into the mechanics of THE CPU and take you through this deeply hidden element.
Do you know groupBy? How is the groupBy statement optimized? What's the principle behind it? Tinker bell takes you from the shallow to the deep, layers of depth, directly hit Linux memory changes!
The Data Definition Language (DDL) of MySQL includes adding or subtracting fields and indexes. Before MySQL 5.6, MySQL DDL operations would copy the original table and modify it accordingly. For example, the DDL operations on table A are as follows: