Oracle

Method One:Sql> explain plan for select name from a A, where a.id=b.id; Sql> select * FROM table (Dbms_xplan. DISPLAY);Method Two:Sql> set autotrace on explain; Open execution plan sql> select name from a, b where a.id=b.id;When you are finished,

Preparation: Upload the Oracle installation software to the Linux system/mnt directory via the FTP tool and unzip the software via the unzip command.-----------------------------------------------------------------------------------------------------

Select A.tablespace_name "Tbsname", 100-round ((NVL (b.bytes_free,0)/a.bytes_alloc) *100,2) "ratio",Round (a.bytes_alloc/1024/1024,2) "Size (m)", Round (NVL (b.bytes_free,0)/1024/1024,2) "Free (m)",Round ((A.BYTES_ALLOC-NVL (b.bytes_free,0))/1024/102

The index of the database if there are more frequent Delete operations, it can cause the index to produce a lot of fragmentation, so, at some point, all indexes need to be re-REBUILD to merge index blocks, reduce fragmentation, and improve query

    set lines 180set pagesize 500col instance_number for  99col module format a10col execs for 999,999,999col etime for  999,999,999.9col avg_etime for 999,999.999col avg_cpu_time for  999,999.999col avg_lio for 999,999,999.9col avg_pio for 9,999,999

1. Start-> Settings-> Control Panel-> Management Tools-> ServicesStop all Oracle Services.2. Start-> Program->oracle-orahome81->oracle installation products->Universal InstallerUninstall all Oracle products, but universal installer cannot be deleted

--v$lock in ID1 when lock mode is TX, the first 2 segments of the physical ID are savedSELECT *From (SELECT S.sid,TRUNC (Id1/power (2,)) RBS,Bitand (ID1, To_number (' ffff ', ' xxxx ')) + 0 slots,Id2 seq,Lmode,RequestS.usernameFrom V$lock L,

Round () functionReturns a numeric value that is the result of rounding operations by the specified number of decimal places syntax round (number, decimal_places) numbers: The numeric value to be rounded up decimal_places: rounding, fractional

1, tree-shaped table, query all the bottom of the recordScenario: Based on the ID of the current record, to query all its child records, each child record then query all child records of the current child record, if any, continue to iterateCurrent

In my opinion, the view of Oracle is used to map the results of the associated query of multiple tables into a "temporary table", and the view is in real time corresponding to the data in the system tables.We can manipulate a view query just like a

This article mainly introduces the use of RowNum and Row_number () in Oracle, as well as the differences and links, very detailed, the need for small partners can refer to.Row_number () over (partition by col1 ORDER by col2) indicates that,

One, ALTER TABLE name modify field type (word length);If not, use the second method:Two--Create tablecreate table TABLE1 ( col1 Number (9), col2 char (20));//attempt to modify ALTER TABLE TABLE1 MODIFY COL1 Number (10 ); --Modification succeeds

1. Use dual with Connect by levelCreate Table as Select as ID from by Level100000;However, there is a limit of connect by level, if exceeding the limit, the system will report, "Connect by Level" Memory is not enough, I tried 10 billion data can,

--1 Import data to the database times the ora-01653:unable to extend table error, online Check the following reason is due to lack of table space;Querying table space Usage statementsSelect a.tablespace_name,a.bytes/1024/1024 Total, (a.bytes-b.bytes)

Environment:Oracle Standalone 11.2.0.4Parameter file location: >show parameter SPFileEdit parameter file: >create pfile= ' D:\init.ora ' from SPFile*.optimizer_index_caching= #这个初始化参数代表一个百分比, the values range from 0 to 99. The default

#useradd oracle-g oinstall-g dbaCreate a new Oracle user, which initially belongs to the Oinstall group (the base group) and also to the DBA Group (additional group).-G: Specifies the starting group to which the user belongs.-G: Specifies the

Interview these days, (during the interview, did not prepare anything, because recently very tired, brought a body past, basically did not take the brain)Well, we're pretty much on the technical side.Let me ask you one more question.A transaction in

--5 constraints, PRIMARY KEY constraints, FOREIGN KEY constraints, UNIQUE constraints, check constraints, non-null constraints.--Add PRIMARY KEY constraint Alter table table_name add constraints Constraint_name Primary key (column_name);--Syntax

1. Change the Chinese folder name to English (use Administrator account, enter the system, after the change, log back to the previous account)A. Enter the "C: \ User" directory to replace "Deng Yi" with "username"B.regeditHKEY_LOCAL_MACHINE\SOFTWARE\

EF Codefirst with ORACLEResolving stored procedures has not found a solutionSo there was no way to use the most basic solution.Using the ADO basic Access class provided by oracle.manageddataaccess, you do not need to refer to the third-party class