Oracle

In Oracle queries, there are times when you want to merge multiple columns into a single row, with the following methods:1. Decode functionThe syntax for the decode function is:　　 Decode (condition, value 1, return value 1, value 2, return value 2,..

Salary: WagesORDER BY: SortDesc: DescendingHire: EmploymentSingle-line functionIt's seven days a week.January is not necessarily 30 daysTrunc: InterceptDual: Empty tableLast: FinallyMonth: MonthsRound: Rounding MethodSUBSTR: String

The default "&" in Sql*plus represents an alternative variable, that is, Sql*plus will ask you to enter an alternate value whenever the symbol appears in the command. This means that you cannot enter a string containing the symbol into a database or

SYS is the highest-privileged OracleDBSNMP: Simple Network Management systemCtrl+d Return to Oracle directory enter exit in SQL can alsoSelect; column where: RowSqlplus/as SYSDBA ENTER SQL Conn hr/hr use HR userLower: Automatically change the case

12. Use the Hosts file to resolve the hostname:# hostnameNode1.test.com# vi/etc/hosts192.168.0.1 node1.test.com Node1Virtual Machines Host# ping Node1 Ping: force echo Request data (used to detect network connections or test network connection speed)

Today, when developing an interface, it is necessary to provide an Oracle user to the interface development company, which can only access the specified table or view and log the process to this1. Create a user for OracleCreate user username

By configuring the Sqlnet.ora file. We are able to change the Oracle login authentication method.Sqlnet. Authentication_services= (NTS); operating system-based authenticationSqlnet. Authentication_services= (NONE); Oracle-based authenticationSqlnet.

Select * fromgoods; AChar(Ten):='Samsung' --Fixed length stringBvarchar2(Ten):='Samsung';--variable StringC Binary_integer:='10001';--signed integer, which optimizes performance for integer calculationsD Number(5,2):='123.45';--valueELong

One: Sql*plus start/close:1.sqlplus/nolog start Sql*plus "Do not connect to the database"2.conn/as SYSDBA Connect to Oracle as a DBA3.startup Startup DatabaseThree ways to start a database and application scenarios1> Normal StartStartup [Open]

1. Add Oracle.ManagedDataAccess.dll2. The instance connecting Oracle is added to the Oracle listener, or the error "Ora-12514:tns: The listener is currently unable to identify the service requested in the connection descriptor " is added as follows,

When importing a DMP file to a database, the following error occurredUpon enquiry, it is due to "The exported dmp file is caused by a different version of the imported database"View the version of the DMP file with Notepad to see if it is consistent

[Oracle Collation] ORA-12705 (character set issues)? . years 5 Month One Day18:11[Oracle collation ]ora-12705 ( Character Set issues )Description: This content is work to use to the knowledge point collation, comes from the work and the network.

Data import times ORA-12899 error, that is, the length of the inserted data exceeds the set length of the field, the actual length is not long, because of the different Oracle character set, the length of the Chinese characters caused by different.

Syntax:SELECT * FROM table_name where DBMS_LOB.INSTR (field name (clod type),' query condition ', ' n ') > 0;Syntax Explanation:In Oracle, you can use the InStr function to judge a string to determine whether it contains the specified character. Its

1. Description1) trigger is a special kind of stored procedure, trigger is usually triggered by the event and cannot accept parameters, memory is called by statement block2) Trigger classification:1.DML triggers: Created on a table, raised by DML

Installing enterprise Oracle databases requires two parts: Oracle RAC, Oracle database. Refer to this article for the Oracle RAC principle. This article is the original introduction of the RAC installation of the actual part, the installation of the

The third part of SQL optimization summary1. Optimization of general principles2. Specific considerations1. General principles of SQL optimization1) Target: Reduce server resource consumption (mainly disk IO)2) Design:1. Rely on the Oracle optimizer

First part knowledge preparation1. SQL Execution Process2. SQL sharing3. Binding variables4. Data table access method5. SQL Execution Order6. Index usage　　　　　　　　　　　　　　　　　　　　　　 1. SQL Execution Process1) Execution ProcessWhen an Oracle instance

0. The Scott User default table describesScott user tables directory contains four tables1. Insert (INSERT) statementTo insert data into a specified column:Insert into Values ("xx");Insert all column data:Insert into Values (x,'xx','lll');2.

1. What is the relational database?A relational model is a model of a database created by a relational model and a two-dimensional table to store data.Oracle,mysql,sqlserver2. What is a NoSQL database?Key-value Saving a databaseHBase, Redis3. Basic