Oracle

Reduce disk I/O Io of distributed Disks Tablespace use local management 1. Distribute files to different devices 1) separate data files from log files 2) reduce disk Io irrelevant to the server 3) evaluate the use of bare Devices 4) Split table data

1. optimizer Mode There are two optimizer modes available for Oracle9i:• Rule-based:-Uses a ranking system-Syntax-and data dictionary-driven• Cost-based:-Chooses least-cost path-Statistics-drivenThe rule-based mode is backward compatible. The cost

As we all know, database design is directly related to the efficiency of database operation. Based on my experience, the rational database design is more effective than upgrading the server hardware configuration for improving database performance.

We have introduced the metadata composed of regular expressions in Oracle, but it is not enough to know the metadata. The regular expressions in Oracle are used in combination with the specific four functions, the most commonly used function is the

Oracle paging query statements can be applied in the format given in this article.   Paging Query format: Select * from(Select a. *, rownum RnFrom (select * From table_name)Where rownum )Where rn> = 21 Select * From table_name indicates

We have introduced the basic metacharacters of Regular Expressions in Oracle and the two common functions regexp_like and regexp_instr. Here we will continue to introduce the remaining two regular expression functions regexp_replace and

InArticleFinally, let's take a look at the performance differences between order by stopkey and order by in the last few pages of page flip queries: SQL> Create Table T as select a. * From dba_objects A, dba_users B, tab; The table has been

ArticleDirectory Questions about Oracle Stored Procedure Basic Oracle Stored Procedure syntax 1. Basic Structure Create or replace procedure(Parameter 1 in number,Parameter 2 in number) IsVariable 1 integer: = 0;Variable 2 date;Begin

  The procedure: Create or replace procedure createsequence(The_seq out number)IsVs_prevyear char (4 );Vs_curyear char (4 );Vs_curseq number; Begin-- Get the year of the latest created changelog recordSelect max (to_char (datecreated, 'yyyy')

Each row of data in an Oracle database table has a unique identifier, or rowid, which is usually used to access data in Oracle. Rowid requires 10 bytes of storage space and is displayed with 18 characters. This value indicates the physical location

This articleArticleAn example shows the performance of the nested loop operation used by paging Query when paging query reaches the last few pages: SQL> Create Table T as select * From dba_users; The table has been created. SQL> Create Table T1

Naming of various data objects in Oracle, including table names, views, and so on, must follow the naming rules of oracle. Oracle naming rules are classified into standard naming and non-standard naming. The standard naming method must meet the

We have introduced a common regexp_like function in the regular expression group in Oracle. Here we will introduce a function regexp_instr. This regular expression function is not used as many as the previous one, but will also be used occasionally.

We have introduced how to useOracleAggregate functions andGroupKeyword to group the result set. A new problem arises. For example, we need to find the grouping results that meet the conditions for the column of the aggregate function. We can

There are many regular expressionsProgramming LanguageAll. Unfortunately, Oracle8i and Oracle9i have been reluctant to join. Fortunately, Oracle10g has finally added the long-awaited regular expression function. You can use the regular expression in

When some tables in the system have highly uneven data distribution, the use of a bar chart can produce better selective evaluation, resulting in a more optimized execution plan. A bar chart provides an effective and simple way to present data

1. It is important to implement distributed and fast access and enrich the memory in Oracle. To avoid page scheduling and switching at any cost, the system global zone (SGA) must be put into the memory every time. Put the SGA in the memory and set

1. Shared Pool tunning The Optimization of the shared pool should be given priority, because a cache miss occurs in the shared pool, which is more costly than the data buffer, because the dictionary data is generally longer than the data stored in

After a DML statement is executed, the results of the DML statement are stored in four cursor attributes, which are used to control the program flow or understand the program status. When running a DML statement, PL/SQL opens a built-in cursor and

The string processing, date functions, mathematical functions, and conversion functions previously introduced in Oracle are also common functions. Mainly include NVL, NVL2, NULLIF, and COALESCE. These functions can be used in various types. The