Oracle

Method 1: SYS @ orcl> select level from dual connect by level select rownum from dba_objects where rownum select to_number (column_value) N from xmltable ('1 to 5'); N ---------- 1 2 3 4 5 Method 4: Select N from (select 1 V from dual) model

(I) modify the value of/etc/oratab to y. [Root @ Rocky ~] # Cat/etc/oratab Orcl:/u01/APP/Oracle/product/10.2.0/db_1: Y(Ii) Modify oracle_home_listner of dbstart to point it to $ ORACLE_HOME [Root @ Rocky bin] # pwd/U01/APP/Oracle/product/10.2.0/db_1/

(I) download and decompress RDA: Click to download [oracle@localhost vmshare]$ gunzip rda_4[1].1-051205.tar.gz[oracle@localhost vmshare]$ tar -xf rda_4[1].1-051205.tar[oracle@localhost vmshare]$ cd rda[oracle@localhost rda]$ lsDISCLAIM.txt

InWhen Sr is sent to Mos, how does v $ segment_statistics update it? ORACLE: V $ segment_statisitcs has been used for internal research since 9ir2 was introduced] (I) first look at the table structure: Sys @ orcl> DESC v $ segment_statistics

MinuteThe design and implementation of regional solutions is a philosophy that pursues comprehensive balance and is full of dialectical unity, It is also an art that accumulates experience and technology. However, vulnerabilities frequently occur in

    1 Definition An executable tool used to analyze Oracle tracking files and generate clearer and more reasonable output results as needed   2 preferences F:\>tkprofUsage: tkprof tracefile outputfile [explain= ] [table= ] [print= ]

In the traditional undo management mode, Oracle treats undo and data block equally. There are three drawbacks: 1) at the beginning of the transaction, the segment header for storing the transaction table is not in memory, and the server process

When data is stored in a data file, its attributes are determined by the storage. These attributes include: in which data file? Which object does it belong? Where is the data block? Row number? These attributes are combined to form the rowid of

Statistics of dynamic sampling are not recorded in the view, and sometimes the tables that have been analyzed are also evaluated. It is effective for CBO because RBO does not need statistics, so dynamic sampling is meaningless. (I) Role of dynamic

(I) histograms Column chart? Histogram? Actually, these two concepts are called here by think directly using histograms. Histograms can be understood as the density and range of the approximate distribution of values in a column) In general, CBO

OracleThis bowl of rice is not good. How many risks are there and how many suggestions are there. 1. Incomplete time point-based Restore, You need to brainwash the control file, tear off the account book (redo log), re-print the account book, this

  SuoThe reference will contain rowid to locate the specific location, but the unique index will not use rowid as part of the "index key" For example, if a non-unique index is created on column col1, the index key is col1 | rowid, so that the index

For exampleIf one day you encounter a special situation, such as the index of the system data dictionary is broken, but you cannot modify this index, because you cannot modify some internal items in the system. You will say, "How nice if I can

Environment: sys@EMREP> select * from v$version;BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - ProdPL/SQL Release 10.2.0.1.0 - ProductionCORE 10.2.0.1.0

Ordered is easy to understand, that is, it means to join the tables following from, from left to right, and to the left as the driver table. Use_nl (T1, T2): Nested cyclic connections are used for table t1 and t2 Association, which does not allow

As a DBA, one of the common scenarios is:Create a tablespace: create tablespace Think datafile '/u01/app/oracle/oradata/orcl/think.dbf' size 100M autoextend on next 10M maxsize 4096M extent management local uniform size 256K segment space

(I) select an appropriate Oracle optimizerDefault Value:9i is choose by defaultThe default value of 10 Gb is all_rows. sys@EMREP> show parameter optimizer_mode NAME TYPE VALUE ----------------

Sometimes, very depressing, ah, what's going on ah, don't take the index, If you find that you do not leave the index, but do not rashly impose your own will, You have to give a reason, do a test first, prove/false take index practical

Let's look at a common phenomenon: HR @ orcl> drop table t purge; Table dropped. HR @ orcl> Create Table T (X number, y varchar2 (30); table created. HR @ orcl> insert into T select rownum, rownum | 'A' from dual connect by rownum Create index idx_

(I) functional index traps When using the function index, you must re-create the function index after the function code is changed. Otherwise, Oracle will return an error but will not prompt you. The test is as follows: HR @ orcl> drop table t