Oracle

In Oracle, null is added or subtracted from a number, and the result is null, Therefore, the nvl () function is used for processing. Declare v_num varchar2 (20); v_num2 varchar2 (20); v_num3 varchar2 (20); v_num4 varchar (20); begin select nvl

In the PL/SQL test window -- Created on 2005-7-3 by tangtianDeclare-- Local variables hereI integer; leftpad varchar (11 );Rightpad varchar (14 );Begin-- Test statements hereSelect lpad ('Hello! ', 8, 'tangtian'), rpad ('Hello! ', 8, 'tang') into

Now there is a Linux server with Oracle installed on it. We want to use the Conn/As sysdba statement to log on to the database and manage the database. However, there is always an error, the error such as service name cannot be found. What is the

Redo file is a very important file in Oracle, if this file is wrong, then oracle will not be able to start normally, the system will report a hateful ORA-00312 error, said the log file has been damaged, so how can we solve it. In fact, it is very

The following is a method for importing Oracle Data to excel on the Internet. I have used it. It is also found that access can directly import Excel data when creating a table, In this way, there is a bridge to convert data between various

The difference between the Oracle database and the MySQL database is what we will introduce in this article, hoping to help you. 1. Group function usage rules In MySQL, group functions can be used at will in select statements. However, if a group

Modifying a project involves modifying many tables in Oracle (including adding, deleting fields, and modifying comments ). As no records are recorded at the beginning, the tables that have been modified are missing during the test. Later, I found

1. create a backup folder in drive D, such as: D:/database backup; create five (up to 7) subdirectories, such as D:/database backup/Monday, D: /database backup/Tuesday ,......, this ensures weekly backup;2. Create five batch files under the

[Db_name :] The unique identifier of a database (Oracle database), which is the Oracle database described in Chapter 1. This expression is sufficient for a single database, but with the popularization of distributed databases composed of multiple

Before Oracle9i, Chinese characters were sorted by binary encoding.The sorting by pinyin, radical, and stroke function is added to Oracle9i. Set the nls_sort ValueSchinese_radical_m is sorted by the beginning (first order) and strokes (Second Order )

In an Oracle database, sequence is equivalent to the serial number. The sequence is automatically increased each time it is obtained. It usually acts on the location where the sequence number needs to be sorted.1. Create Sequence (Note: you need the

Oracle exception in the predefined description Oracle error exception informationORA-0001 dup_val_on_index tries to break a unique limitORA-0051 timeout-on-resource timeout while waiting for resourcesThe ORA-0061 transaction-backed-out is canceled

1. dataguard PrincipleOnce standby is created, mongouard will pass the redo of the primary database to the standby database, and then apply redo in standby to synchronize the database. There are two types of standby: Physical standby and logical

Instr (Source string, target string, start position, matching serial number) In Oracle/PLSQL, The instr function returns the position of the string to be truncated in the source string. Only retrieval once, that is, starting from the character It

OverviewIn the Oracle installation directory $ home/Network/admin, sqlnet is often seen. ora tnsnames. ora listener. ora files except tnsnames. ora, the detailed usage of the other two files is not well understood by many people.Sqlnet. ora is used

The main process of SQL parsing in Oracle: The cursor concept we mentioned is complicated. It can be a cursor in a client program, a private cursor in a service process, and a shared cursor in a server shared pool. If a cursor is opened, its

When using adoquery of Delphi to connect to the Oracle database, NOTE: When SQL contains multiple case when, you must add an arc. Otherwise, an exception or CPU debugging will be reported directly.The problem is very strange. If the same SQL

View the lock table process SQL statement 1:Select sess. Sid,Sess. Serial #,Lo. oracle_username,Lo. OS _user_name,AO. object_name,Lo. locked_modeFrom v $ locked_object Lo,Dba_objects AO,V $ session sessWhere ao. object_id = Lo. object_id and Lo.

How to Use select top in different databases:   1. Oracle Database (Oracle does not support the select top statement. Therefore, the combination of order by and rownum is often used in Oracle to query the select Top N)   SELECT *

\" 1. View All Users Select * From all_users; ------- view all users Select * From user_users; -------- view current user 2. View user or role system permissions: Select * From user_sys_privs; -------- view permissions of the current user 3. view