Oracle

Indexes have a great effect on the performance of database access, and designing a reasonable index is very important for system performance adjustment. Using indexes is the most difficult point in the database development process. There are several

We know that in the database, the Chinese character occupies two bytes, while the other characters occupy a byte, so the comparison of two functions can determine whether there is Chinese, Length calculates character lengths, LENGTHB calculates byte

Quote Your friends blog: http://www.blogjava.net/amigoxie/archive/2010/05/21/321542.html one. Oracle Server Installation Recently Ann mm asked me 2 years ago to write a simple Oracle data import the entire document, afraid to find out later, or

Under Linux to start Oracle and in Windows is different, for general in Windows operating habits people have a lot of not adapt, so I write this article to facilitate the novice to operate, the following step-by-step to explain the start process. 1.

If I hadn't used the Oracle lead this time, I wouldn't have found anything so useful. Oracle statistical analysis function lead Syntax structure: Leads (value_expr [, Offset][,default]) over ([Query_partition_clause] ORDER by

The minus directive is used on two SQL statements. It first finds the results of the first SQL statement and then looks at the results of the second SQL statement. If so, the information is removed, not in the final results. If the result of the

There are two types of annotations in Oracle First: "--" to annotate a line The second: The beginning of the annotation "/*", the end of "* *" can be annotated multiple lines. =================================================================

A. Modifying an Oracle instance under Windows platform does not start with the service: 1, modify the registry key value to achieve the following:Hkey_local_machine\software\oracle\key_oradb10g_home1 2, found on the right to find the

Table joins in three different ways: sort merge joins (sort merge join), nested loops joins (Nested Loops join), Hash joins (hash join). 1. Sort merge joins (sort merge Join) The execution of the sort merge join IS as follows: * Sort the rows of

The basic principles of cursors: In Oracle, when a pl/sql block of a SELECT, INSERT, update, and DELETE statement is executed, Oracle assigns a buffer to it in memory, puts the execution result in the buffer, and the cursor is a pointer to it.

Sometimes we need to migrate the data of the database, but some data will not let the migration in the case of partial table export Import. ----Data export--Create a directory to put DMP filesMkdir-p/backup/oracle/dmp --Assign value to Oracle

Functions in an Oracle database A: Table name, B: The name of the field to be modified Update A Set B = replace (b, ' null ', ' 0 ') where id = ' 5644 '; The execution effect is as follows: The use of Decode functions The function is--the time of

Trigger TRIGGER Always poison not invade I unexpectedly in this joint eye on the cold, the head is also dizzy, a confused don't know what to think, thief uncomfortable, cough cough cough.Today, another basic object in the Oralce database-triggers,

The following EMP table is a table with ORCL database instances. Before executing a stored procedure, you must first execute SET serveroutput on; Show error; You can display specific execution error messages.1. With no parameters A. Create A

1. Creating a tablespace Create tablespace example_tablespace datafile ' e:\****.dbf ' size 100m reuse autoextend on next 10m maxsize Unlim ited; 2. Create user, specify table space, temporary tablespace Create user username identified by password

Definition and operation of Oracle transaction, process, and function transactions 1. The characteristics of the transaction acid:2. Atomicity (atomicity): The statement that makes up a transaction forms a logical single Yuan, you cannot only

How the problem determines whether a field exists in a table. Note: The table name and field name must be capitalized, otherwise the result is incorrectOne: Check table name:Select COUNT (*) from user_tables where table_name = table name (uppercase);

Download the installation package from the following website and choose your own version Http://www.oracle.com/technetwork/topics/linuxx86-64soft-092277.html Download the client and Sqlplus programs from the Oracle official website. Take 11g as an

some tips on creating Oracle Dblink process Two different database servers, one user from one database server reading the data of a user under another database server, this time can use Dblink.Actually Dblink and the database view is similar,

Export and Export user objects:1. Plsql log in to the database2. Query the default tablespace for the current user (take DEMO1 account as an example)With DEMO1 user login plsql, in the window of the users branch to find the current user name DEMO1,