how to use dblink in oracle sql

) Identify the SQL statement for ' inefficient execution ':While there are a variety of graphical tools for sqlseo/' target= ' _blank ' > optimization, writing your own SQL tools to solve problems is always the best approach:SELECT executions, disk_reads, Buffer_gets,ROUND ((buffer_gets-disk_reads)/buffer_gets,2) Hit_radio,ROUND (disk_reads/executions,2) Reads_per_run,Sql_textFrom V$sqlareaWHERE executions>

only provides caching (cache BUFFERIILG) for simple tables, which does not apply to multi-table connection queries. The database administrator must set the appropriate parameters for this zone in the startup parameters file, and the larger the memory area, the more statements can be preserved, and the greater the likelihood of being shared. When an SQL statement is submitted to Oracle,

1 Introduction to null valuesNULL is a unique data type in the database. If a column in a record is NULL, the value of this column is unknown and uncertain. Since it is unknown, there are several possibilities. Therefore, NULL is not a definite value. This is the origin and basis of NULL. The results of all NULL-related operations can be derived from the concept of NULL.2 Introduction to null values in oracleWhen you do not know the specific data, it is unknown. You can

by other users after you create it, delete it when you disconnect it. If the table is createdOtherwise, SQL Server deletes the table after all users are disconnected.Different:1. the SQL SERVER temporary TABLE is a "memory TABLE", which is stored in the memory. The ORACLE temporary TABLE is stored in the data dictionary unless DROP TABLE is executed.2.

Oracle pl/SQL programming the use of SQL statements select must have a return record, do not report an error saying that no data is found and must have an into select statement to return one and only one record cannot be written as where deptno = 10 because multiple records will be returned. Of course, the record menti

', srcdir^' Dbstatus.txt '); endif Abort endifElseSMSG ="Error updating database, point" is "open log file and exit the installation, click" No "to exit the installation directly. /n "; SMSG = smsg+"If errors can be ignored, select the database type" None "to skip database updates and update the program directly,/n"; SMSG = smsg+"Then execute the SQL script manually in the database (saved in the script directory a

How to use Oracle to conveniently view alarm log errors and oracle logs I checked the information on the Internet for a few days and tried to clear the alarm log Content and create an external table to solve this problem. I. Back up and clear alarm logs Back up the daily alarm logs and clear them. 1: Back up alarm logs Under the $ ORACLE_HOME/SID/bdump/directory,

passwords and accounts are the first guarantee of database security. For example, when creating an Oracle database user name, it has Password Complexity verification settings by default. If we set the password to "123456" when creating the user name, the Oracle database will not accept it. The password is too simple and easy to crack. Microsoft SQL Server databa

). The execution part is required, and the other two parts are optional. The basic structure of Oracle PL/SQL block is composed of three parts, regardless of the size of the Code. 2. Control StructureThe Oracle PL/SQL program segment has three program structures: Conditional structure, cyclic structure, and sequential

= E. dept_no(Efficient ):Select dept_no, dept_name from Dept d Where exists (select 'x'From EMP e where E. dept_no = D. dept_no ); (19) SQL statements are written in uppercase. Because Oracle always parses SQL statements first, converts lowercase letters to uppercase and then executes them. (20) In Java Code Try to use