Oracle

Isnull () in sqlserver () Nvl () in Oracle () Nvl (expr1, expr2) If expr1 is null, the value of expr2 is returned; otherwise, the value of expr1 is returned. Nvl2 (expr1, expr2, expr3) If expr1 is not null, the value of expr2 is returned;

1. What is a bare device? A bare device, also called a raw partition, is a special character device that is not formatted and not read by UNIX through a file system. It consists of applications Program Reads and writes data. It is not buffered by

There are many application projects. At the beginning, MySQL Databases can basically meet various functional requirements. As the number of application users increases and the amount of data increases, MySQL gradually becomes overwhelmed: the

Predefined roles: 1. Connect role: Typical and basic rights granted to end usersAlter session -- modify a sessionCreate Cluster -- create a clusterCreate database link -- create a database linkCreate sequence -- create a sequenceCreate session -

Author: gnuhpcSource: http://www.cnblogs.com/gnuhpc/ TLS, 1 p. MRS. Transport htyQuogue, Long Island16 September 1962, SundayMy dear:Well, here we are-but not here. you at st. tim's, sister in Princeton, and me in Quogue, and another brand new year

In my opinion, whether B/S or C/S is developed in any business system, the core focus should be on processing logic and high performance and security, the underlying layer and system structure should be well considered by the architect to form a

This is a virtual table. You can use this table when operating most Oracle Objects, such as sequence and sysdate.For example, select sysdate from dualSelect seq1.nextval from dualAnd so on. 1. Dual is created by SQL. bsq. When each database is

Hints is a mechanism provided by Oracle to manually specify the execution plan of SQL statements for hint writing. It is used to tell the optimizer to generate an execution plan in the way we tell it. We can use hints to achieve: 1) Type of

ORACLE:   Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> DEPARTMENT_ID_SEQ     MySQL: MSSQL:   Code highlighting produced by Actipro CodeHighlighter

In Oracle databases, undo has three major functions: providing consistent read, rollback transaction, and instance recovery). Consistent read is relative to dirty read (dirtyRead. Assume that a table t contains 10000 records. It takes 15 minutes to

From Oracle 9i, You can monitor the usage of Oracle indexes by using the following methods: Alter index . monitoring usage; After enabling monitoring for an index, you can check whether the index is used: To disable INDEX usage monitoring, use the

1. Physical Structure (composed of control files, data files, redo log files, parameter files, archive files, and password files)　　 The data in a database is stored in physical files on the disk. When used, the data is transferred to the

Why cursor: First look at this: Declare v_empno EMP. empno % type; v_ename EMP. ename % type; begin select empno, ename into v_ename, v_empno from EMP; dbms_output.put_line (v_empno | ''| v_ename); end;This SELECT statement may return

1. Define the stored procedure of Oracle with output cursor. The output cursor definition type is sys_refcursor.1 create or replace procedure sp_demo ( 2 emp_no in varchar2, 3 o_res1 out varchar2, 4 o_res2 out varchar2, 5 o_ds1 out sys_refcursor, 6

Example: PID IDA BA cA EB B1B B2C C1E E1E E3D D1Specify pid = A and selectA BA cA EB B1B B2C C1E E1E E3SQL statement: Select parent, child from Test start with PID = 'A'Connect by prior id = PID     OracleSQLRecursive query:1. Table StructureSQL>

Incremental ORACLE data backup/ExportThe following describes how to use the Export/Import utility to back up and restore an Oracle database: Incremental unload/load. Incremental detaching is a common data backup method, which includes three

1, Select 'drop table' | table_name | ';'From all_tablesWhere owner = 'username to be deleted (uppercase )'; 2, Delete all tables Take user test as an Example For example: DeclareCursor cur1 is select table_name from dba_tables where owner = 'test ';

Table creation statement:Begin Execute immediate 'drop table customer '; Exception when others then NULL; End;   BeginExecute immediate 'drop table orderhistory ';Exception when others thenNULL;End; -- Create Customer tableCreate Table MERs(Customer_

Document directory V $ session_longops V $ session_longops This view shows the status of operations that have been running for more than 6 seconds. This includes backup, recovery, statistics collection, and query.   To monitor the query progress,

Oracle import utility allows you to extract data from a database and write the data to an operating system file. The basic format used by IMP: Imp [username [/password [@ Service]. The following describes common usage of imp. 1. Get help imp