In order to facilitate learning and testing, all the examples are built under Oracle's own user Scott.
Note: The red order by in the title indicates that order by must be taken when using this method.1. rank ()/ dense_rank () over (partition by... Order by...)
Now customers have such a need to query the information of t ...
Added by Dragonfly on Thu, 16 May 2019 05:30:30 +0300
Added by wiggly81 on Thu, 16 May 2019 00:18:55 +0300
Brief: The eighth day was recorded today (only eight days were written).Sometimes I see more, sometimes I see less, and then I save a few days to write together.Today, I wrote this plugin for an afternoon yesterday. I went back after work. I ended it today and added a process diagram to help understand the following principles.I have been readi ...
Added by tmaiden on Wed, 15 May 2019 23:32:20 +0300
General database role privilege handling in SQL Server Recently, we have been doing database privilege cleanup with colleagues, mainly by deleting some accounts, removing the larger privileges of some accounts, etc. For example, some have db_owner privileges, we remove the database role db_owner of the accounts and grant the minimum required ...
Added by Karpathos on Wed, 15 May 2019 18:59:55 +0300
1.java.lang.NullPointerException (Runtime Exception) is a runtime exception that the compiler cannot predict, such as when you define a Reference variable String a, but you did not instantiate the variable with the new keyword.
There are two solutions to this null pointer exception, because you call this a's method againif(null!=a) this variabl ...
PostgreSQL, brin index, gin index, merge delay, gin_pending_list_limit, query performance degradation
GIN index is an inverted index of PostgreSQL database with multi-value type. A record may involve KEY in multiple GIN indexes. So if index is merged in real time when writing, IO will increase sharply and RT will increase in ...
Added by hatching on Wed, 15 May 2019 09:30:25 +0300
We've already talked about it Principle and algorithm of MySQL InnoDB index Here's how to manage and use B+tree indexes and some new features.
Management of B+Tree Index
The basic indexes we use in the InnoDB engine are B+tree indexes.
Create and delete indexes
It can be created and deleted in two ways:
# Mode 1: alter table, in which case bot ...
Added by ehhwan on Wed, 15 May 2019 05:12:03 +0300
Oracle Kernel Technology Disclosure_Lv Haibo's Learning Notes
When Cache Buffers Chain(CBC) Latch is competing, there are two main situations:
1. Multiple incompatible processes apply for the same CBC Latch to access different Buffer Headers (BH) of different chain lists protected by this CBC Latch, which is called hot chain c ...
Added by PHP Monkeh on Tue, 14 May 2019 18:13:35 +0300
Introducing modules into files
Used to establish connection with database
Create object: call connect() method
Conn = connect (parameter list)
Parameter host: connected mysql host, if the local host is'localhost'
Parametric port: The port of the mysql host connected by default is 330 ...
PostgreSQL, pgbench, tpcb, tpcc, tpch, lvm2, zfs, bands
Several recent PostgreSQL OLTP and OLAP tests:
PostgreSQL 11 tpcc Test (103,000 tpmC on ECS) - use sysbench-tpcc by Percona-Lab
(TPC-H test SF=10,SF=200) PostgreSQL 11 vs 10 vs Deepgreen
PostgreSQL 10 billion tpcb performance on ECS
PostgreSQL on Aliyun ECS + ESSD - 100 ...
Added by stanleycwb on Tue, 14 May 2019 14:43:51 +0300