Oracle

Today, a friend asked me if I could query the physical files that were actually stored in the table or index. Tables, indexes all have corresponding segment. Segment is the concept of physical storage, and tables and indexes are logical concepts. A

If you want to analyze a performance problem with a SQL, you usually have to look at the SQL execution plan to see if there is a problem with every step of the SQL execution. If a SQL is normally performed well, but one day suddenly performance is

The Oracle execution plan has 5 types of index scans, depending on the type of the index and the where constraints, namely, index unique scans (the index unique scan), index range scans (the index range Scan), index full scan Scan), Indexing Quick

When querying the data, SQL Server is not case-sensitive by default. If you want to differentiate, you need additional settings. Oracle is case sensitive by default. If you don't differentiate, you need additional settings. The following are

equality in Oracle is =, inequality is!= and <>   1. The use of 1<>1: For situations where the structure does not take data, for example: CREATE TABLE Table_temp tablespace tbs_temp as SELECT * from Table_ori where 1<>1 Build a table

Approximate process. Oracle Log Analyzer Tool Logminer use 1. Set Date format Alter system set nls_date_format= ' Yyyy-mm-dd hh24:mi:ss ' scope=spfile; Select To_char (sysdate, ' Yyyy-mm-dd hh24:mi:ss ') from dual; 2. Add Supplemental Log If the

The solution to the failure of PowerDesigner15 to connect to Oracle is the first thing we want to introduce in this article: A table was designed in PowerDesigner15, Then you want to connect Oracle through the process PowerDesigner, and then

There is a new feature in 11G that does not allocate segment when there is no data in the table to save space Workaround: 　1, insert a line, and then rollback will produce segment. The method is to insert data in an empty table and then delete it,

Oracle and RAW Device FAQ1. What is called a bare device.A bare device, also called a bare partition (raw partition), is a special character device that is not formatted and is not read by UNIX through a file system. It is the responsibility of the

1, through the top tool to check the system memory and swap usage (including process information). $top 2, view the user of the process connection.$ps-ef|grep Process Number 3, delete the EMP table Empno 2201 of the row record.Sql>delete from EMP

Knowledge Points: 1.Oracle database is a relational database management system developed by Oracle (Oracle/shen Domain), which is one of the most widely used databases in the world at present. The main version is oracle9i,oracle10g,oracle11g,oracle12

RowNum is a pseudo column that Oracle has provided from 8, numbering the results of SQL, always starting at 1, with the common use of paging output. Like what: SELECT * from table_temp t WHERE rownum SELECT * FROM (select A.*, rownum rn

Original URL: http://blog.sina.com.cn/s/blog_7e4ac8b50100vcwv.html Parsing and execution order of the SQL condition field (Where part) [Right--> left]Experiment one: It is proved that the parsing of SQL is from right to leftThe following experiment

DBA View Serial number 1 Dba_data_files Information about the database file 2 Dba_db_links All database links in the database 3 Dba_extents Include all partitions in

type of 1.ORACLE optimizer Rule---------based on rules Cost---------based on costs CHOOSE-----Selectivity Set the default optimizer to pass various declarations of optimizer_mode parameters in the Init.ora file, such as

The database server character Set select * from Nls_database_parameters, which originates from props$, is the character set representing the database.The client character set environment select * from Nls_instance_parameters, which originates from V$

When writing SQL in order to count or to sort the data, we will encounter the need for a column of data consistent, b column of data to order the largest column B data this situation. So how do we write SQL in this situation? We can follow our

1.6 Oracle Installation Prerequisites The following actions are logged on to the RacNode1 node with root. If you do not use DNS, you must configure the/etc/hosts file as follows Note: Even if the scan address is defined in the/etc/hosts file,

This paper describes the method of Oracle cross-database query through the creation database link 1. Configure the local database server's Tnsnames.ora file $vi $ORACLE _home/network/admin/tnsnames.ora Add the following line, where Dblink is the

Oracle creates table spaces, creates users, and authorizesAfter Oracle is installed, there is a default database in which we can create our own database, in addition to the default database.To avoid the hassle, you can create a database with the '