Oracle

Oracle NET1. The client obtains the specific connection information of the server through the @ora10g name to the Tnsname.ora file.2. The client sends a link request to the server via the description in the Tnsname.ora server side3. After the server'

first, the common view descriptionOracle SQL statement resource consumption monitoring, the most commonly used system views are:V$sqlV$sqlareaV$sqltextV$sessionV$sql and V$sqlarea are basically the same, documenting the SQL statistics in the shared

User ManagementAuthentication: AuthenticationAaa:Authentication: AuthenticationAuthorization: Rights ManagementAudition: AuditGrant: Authorizationunset: Undo (Eliminate)Sql>echo $ORACLE _sid ORCL query database is named ORCLSql>vnset ORACLE_SID

About DMP Files We use more, DMP files It is used as the file format for the Oracle Import and export tables, and today the DMP files are exported and imported for learning.DMP file ExportDMP file export is generally three kinds, they are: export

1. What is NULL?Null means Unknow (unknown), which does not mean whatever the value is.For example, a column in a row does not have any value or null.Oracle agrees that no matter what type of data the field is empty, in addition to the following two

A requirement is a record of logged-in logs logged by a user, including time and connection IP addresses, and connections, which can help keep track of analysis issues, especially if some human-induced DML operations cause data loss, data clutter,

Collection OperationsSelect employee_id, job_id from EmployeesUNION ALL does not remove reserved duplicate valuesSelect employee_id, job_id from Job_history;Select employee_id, job_id from EmployeesUnion removes duplicate valuesSelect employee_id,

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① log in to the database with the ' sys ' user, enter select * from dba_users; see if there are any Scott users, as shown in:650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M01/9D/5E/wKioL1l-8maBmLr0AABqgUF9CR8135.png "title=" Qq2017073117021

The permission system of Oracle database is divided into System permission and object permission. System permissions (Database system privilege) allow the user to execute a specific set of commands. For example, the CREATE TABLE permission allows a

Grouping Functions , multi-line functions Summary of non-null dataOnly Lieri the null value first.Grouping is not requiredSql> Select COUNT (*), sum (Salary), AVG (Salary), min (Salary), Max (salary) from employees;sql> CREATE TABLE t1 (x int);sql>

=========================oracle Database Simple Statement ============--%type type--sql> declare var_name varchar2 (--zm_tree); Fname%type; Var_type varchar2 (+);--zm_tree. Flinktype%type; Begin SELECT T.fname,t.flinktype to Var_name,var_type from

single-line functionSql> Select Upper (first_name), Lower (last_name), Length (last_name) from employees;Sql> Select (sysdate-hire_date)/7 from employees;Sql> Select Trunc ((sysdate-hire_date)/30, 0) from employees;Sql> Select Trunc (Months_between (

Exporting data using exp and EXPDP1.exp Export Data CommandExp gd_base/@192.168. 13.211 file=d:\export\gd_base.dmp log=d:\export\gd_base.log full=y2.EXPDP Exporting data(1) CMD window to connect to database, go to Sqlplus pageSqlplus Sys/[email

Dual is a virtual table that makes up the syntax rules for SELECT, and Oracle guarantees that there will always be only one record in dual. We can use it to do a lot of things, as follows:1. To view the current user, you can execute the following

We all know that after the Oracle database installation is complete. By default, there are several system roles or permissions. Nomal,sysdba,sysoper Wait, every time you log in to Oracle. are directly logged in as Conn/as sysdba. But I never know

just like completing the JDK installation, you need to configure the environment variable java_home and path for the system to let the system know the Javac command inside the JDK. Similarly, there is a process required to install Oracle. When you

For Oracle's self-increment column, use the serial number (sequence).Initialization phase to manually establish a sequence, and then insert the time, but also to manually read the sequence nextval assigned to the relevant fields, such as ID, the

There are two ways in which JDBC connects to an Oracle database: Connection Database SID Connecting to a database service_name When the SID is connected, the string is as follows:URL="Jdbc:oracle:thin:@192." 168.56. :1521: orcl1

The NVL () function, which handles NULL.Decode () function,: Majority value judgmentDecode (value \ column, Judge value 1, display value 1, Judge value 2, display value 2) If the judgment value is not included, the display is emptyThe Decode ()