A cursor is a memory workspace of SQL, defined by the system or user as a variable. The function of cursors is to temporarily store blocks of data extracted from databases. In some cases, data needs to be transferred from tables stored on disk to computer memory for processing, and finally the processing results are displayed or ...
Posted by lillyapps on Sat, 18 May 2019 01:36:31 -0700
* JDBC is a bridge for Java to operate database. With the help of the data-driven provided by the database and the database language to be operated on, After executing the database statement, you can crud the records in the database.*
See the demo case of linking mysql database to simulate landing:
Case 1: SQL injection, deceiving th ...
Posted by DedoMraz on Sat, 18 May 2019 01:06:43 -0700
PostgreSQL, citus, new objects, new databases, new users
citus is a plug-in of PG. The plug-in mainly deals with ordinary SQL (non-UTILITY) plus HOOK, and uses UDF to create new partitions for tables.
If the user wants to execute DDL, then CITUS can not take over, how should it operate?
In two cases, one needs to be executed ...
Posted by ThEoNeTrUeAcE on Fri, 17 May 2019 15:47:15 -0700
This paper contains the following two knowledge points. The environmental information is shown in the following figure:
Deploy Data Guard service;
Configuration and use of Data Guard Broker.I. Deployment of Physical Standby
1.1 Main Library Preparations
1.1.1 Enable force logging
SQL> ALTER DATABASE FORCE LOGGING;
1.1.2 Create standby data ...
Posted by alin19 on Fri, 17 May 2019 08:49:27 -0700
How to implement a "accessory person" or a nearby "store" function?
It can be done based on the database, given a coordinate, with this coordinate as the radius r, j uses sql to select the elements of the approximate circle for display.
select id from positions where x > x0- ...
Posted by raan79 on Fri, 17 May 2019 03:42:24 -0700
After more than three months, I finally remember that I still have a blog. Actually, I don't forget it. I just don't have time to write a blog when I'm busy at work. So I'll make time tonight to record a problem I encountered in my last job and share it with my garden friends so as to avoid going into a hole.
Last week, JdbcTemplate execute ...
There are three processes to start oracle, nomount, mount, open
I. nomount stage
During the nomount phase, you can see that the instance has started.The oracle process creates a shared memory pool based on the parameter file.
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 1653518336 bytes
Fixed Size 22138 ...
Posted by JellyFish on Thu, 16 May 2019 16:56:20 -0700
### Caching and Query Sets
Each QuerySet contains a cache to reduce the actual operation on the database. Understanding this concept will help you improve query efficiency.
For the newly created QuerySet, its cache is empty. When the QuerySet is first submitted, the database performs the actual query operation. Django stores the results of the ...
Posted by stephenalistoun on Thu, 16 May 2019 15:05:03 -0700