Oracle

We know that the normal execution of select Sysdate from dual in the Oracle database can return the system time of the current host.When the system time is changed normally, the corresponding query result becomes the modified system time.Now there

In Oracle 11g, Oracle added 2 queries: Pivot (row to column) and Unpivot (column change)Pivot (aggregate function for column name in (type)), where in (") you can specify an alias, in, you can also specify a subqueryRow to column:SELECT * from

1, under normal circumstances, we are not access to Ojdbc.jar, need to establish a local warehouse.2, first find your own Oracle Ojdbc.jar put it into the C:\Users\Administrator directory, and then execute the following codeMVN

1. View the log file location.[email protected]>select inst_id,name,value from V$diag_info;inst_id NAME VALUE---------- -------------------- --------------------------------------------------1 Diag Enabled TRUE1 ADR base/u01/app/oracle1 ADR Home/u01/

Advantages of using Views:1. Simplify data manipulation: Views Simplify how users work with data.2. Focus on specific data: unnecessary data or sensitive data can not be present in the view.3. The view provides a simple and effective security

1. Knowledge points--First stored procedure/* Print Hello worldcreate [or replace] PROCEDURE procedure name (list) as Plsql subroutine body; Call stored procedure: 1. exec SayHelloWorld (); 2. Begin SayHelloWorld (); SayHelloWorld (); End /*

To see the 2 differences more clearly, look at the following table: UNDO REDO Record of How to undo a change How to reproduce a change Used for Rollback, Read-consistency Rolling forward DB changes

The new feature after oracle11g makes it possible to omit empty tables when allocating table spaces by default, to reduce the resource usage of tablespaces, so that empty tables are ignored when exporting user data using the EXP export of Oracle,

---a single index reset statementAlter index INDEXNAME rebuild;---Querying Data Index object statementsSELECT * from User_indexes;------The index of the database (the index containing the $ character cannot be rebuilt) bulk generate index Reset

The main contents include:(1) Three kinds of cycles and their simplification(2) Use of cursors(3) Exception handling(4) Stored procedures(5) Storage function(6) Trigger(7) Other PL/SQL operationsDefine variables---------------Loop loop---------------

Oracle numbernumber [(P [, S])]Number has precision p and scale s. theprecision p can range from 1 to 38. The scale S can range from-84 to 127. Bothprecision and scale is in decimal digits. A number value requires from 1 to 22bytes.the scale is

The syntax for merge is as follows:MERGE [hint] into [schema.] table [T_alias] USING [schema.] {Table | view | subquery} [T_alias] On (condition) when matched and merge_update_clause when not matched then merge_insert_clause;What is merge and how is

Oracle base data Type (4 classes):Character Type: stringCHAR (max.), nchar (max 1000, Unicode supported)---> fixed length, fixed length even if not full it automatically occupies these positionsVARCHAR2 (Max 4000), NVARCHAR2 (Max 2000, Unicode

 prefix Dba_: Contains all object information for the DB instance. V$_: The dynamic view of the current instance, including the views used by system management and system optimization. User_: Records the user's object information.

Introduction to Oracle Trunc function usageCore TIP: Introduction to Oracle Trunc function usage1.TRUNC (for dates)The date value that the Trunc function truncates for the specified element.Its specific syntax format is as follows:TRUNC

1,oracle no offet,limit, in MySQL we use them to control the number of rows displayed, most of it is paging. If Oracle is paging, replace it with RowNum.2,oracle Build the table, there is no auto_increment, all want to let the table of a field

Recently in order to improve efficiency in the company's business to do mybatis batch update, but to the Oracle database did not succeed in several times, and later found that mybatis the last missing a semicolon, may be mybatis internal do an

1. query Table Space LocationSELECT * from Dba_data_files;-d:\app\administrator\oradata\orcl\***.dbf2. View Temporary tablespace locationsSELECT * FROM V$tempfile-d:\app\administrator\oradata\orcl\***_tmp.dbf3. Create a temporary table spaceCreate

The key role of Oracle 10g database:1, reduce management costs;2, improve performance;Enhancements to Oracle 10g include:1, high availability enhancement, new flashback ability, support rollback update operation;2, to enhance the security, easy to

1,Oracle's parser according to right-to-left order the table name in the FROM clause is processed, so that the last table written in the FROM clause (the underlying table, driving tables) will be processed first . In the case that the FROM clause