MySQL Subquery Derived Table, Subquery Error

  From MySQL 5.7 ref: 13.2.10.8 Derived Tables   8. Derived Table Derived tables are expressions used to generate tables within the scope of a query's FROM clause. For example, a subquery in the FROM clause of a SELECT query is a derived table. SELECT ... FROM (subquery) [AS] tbl_name ... The [AS] tbl_name clause is required because ...

Posted on Sun, 02 Jun 2019 09:36:59 -0700 by supermerc

The Use of Path Key and Index in PgSQL Source Analysis PG Optimizer in Sorting

outline The processing of SQL in PostgreSQL is similar to that in pipeline mode, which is successively made up of: Lexical and grammatical parsing. After generating parsing tree, it is handed over to semantic parsing. Semantic parsing, generating query tree, and handing it to Planner Planner generates an execution plan based on the query ...

Posted on Sat, 01 Jun 2019 15:42:50 -0700 by Muppet9010

The Way to Self-redemption--Java (Data Processing)

Simple Data Processing Recently, we did a project to import the data from execl into the data and analyze the manufacturing data. In fact, we don't care what kind of data we want, just like you, I only care about the technical points and the functions we want to achieve. Come on, let's talk about technology. execl data imported into databa ...

Posted on Fri, 31 May 2019 17:31:21 -0700 by mlewczuk

Oracle exp/imp imports different table spaces

In Oracle database table migration, we usually have this requirement. In the development stage, all users'data may be placed in one table space, such as users table space. But in production, we want to put each user's data in different table spaces. At this time, using exp/imp directly does not have the function of selecting table space (expdp/ ...

Posted on Thu, 30 May 2019 11:17:27 -0700 by Scrank.com

Zsh Development Guide (Part 18 More Use of Built-in Modules)

Guide reading In addition to zsh/mathfunc, zsh/net/socket, zsh/net/tcp, Zsh also has some other built-in modules. In this paper, we will briefly talk about several commonly used modules. How to Use Modules # Use zmodload plus module name to load modules % zmodload zsh/mathfunc # If you don't add parameters, you can view the modules that are lo ...

Posted on Mon, 27 May 2019 17:02:14 -0700 by sawade

QL optimization experience with twists and turns (photo edition)

background Recently, I received an SQL tuning task, which performs nearly five seconds in a month of data statistics in the development environment. Originally thought it was a smooth optimization, but I didn't expect that in order to get the best result, it went through twists and turns. First impression Initial slow SQL select case wh ...

Posted on Mon, 27 May 2019 16:13:42 -0700 by MrBiz

Online version gray publishing strategy

        From the beginning of contact with operation and maintenance, the most pressing thing is to put the business on line. Why do you say so? It's because there are so many big pit teammates. Either because of the missing code of children's shoes developed, or because of the inadequate testing of child ...

Posted on Mon, 27 May 2019 15:24:44 -0700 by Sudden

linux changes mysql data storage directory

Generally stored under / var/lib/mysql 1. View mysql's current data storage location [root@dlzx ~]# mysqladmin -u root -p variables |grep datadir Enter password: | datadir | /usr/local/mysql/data/ | [root@d ...

Posted on Mon, 27 May 2019 14:18:10 -0700 by EvilSupahFly

php file export full records

date: 2017-9-4 01:25:27 title: php file export full records Almost all of phper's needs come from the "management backstage", of which "file export function" is almost indispensable. After three years of phper, almost three years of this requirement has been followed. Recently, although I'm writing a server, since the little ...

Posted on Mon, 27 May 2019 12:35:55 -0700 by flyersman

Mycat Realizes Reading and Writing Separation of Mysql Database

I. overview Mycat's role in applications is described as follows: Mysql master is responsible for reading and writing for master library and Mysql slave is responsible for reading from slave library. In this way, programmers can only care about business code compilation, without worrying about load balancing of back-end database cluster, separa ...

Posted on Mon, 27 May 2019 10:56:43 -0700 by robert.access