Oracle

If Oracle group by does not have an index, it performs a full table scan, resulting in poor performance. To improve performance, note the following: 1. After filtering, group again. That is to say, use having as little as possible to allow him to

Preface:Is null the same as zero (0? Of course not. Null indicates that it does not exist or is not sure. 0 indicates no. In the development of the application hibernate, a problem occurs: a field in the Oracle database (number type) has no value (

Recently, I was working on upgrading the company's internal system. The original system does not require encryption of passwords. Now I need MD5 encryption.   Oracle Database Password MD5 encryption, Oracle provides the MD5 encryption function.

Do not consider hardware restrictions, such as memory and storage. How many records can a table store theoretically?   Hypothesis: A tablespace contains 1022 datafiles, The maximum size of a single datafile is 32 GB. Assume that each block is 1

1. query student addresses in BeijingSelect student_id, student_nameFrom studentsWhere contains (address, 'beijing ')Remark: Beijing is a word that must be enclosed in single quotes. 2. query student addresses in Hebei ProvinceSelect student_id,

Common Oracle third-party tools include SQL plus, PLSQL developer, Object Browser, Toad, Embarcadero rapidsql,Haha now we have a new dbtool, which is quite powerful. Let's use it. I have been using PLSQL developer for a long time, but sometimes it

  Grant alter system to SA;Grant select on V _ $ lock to SA;Grant select on all_objects to SA; Create or replace procedure d_debugAsV_index varchar2 (40 );V_table varchar2 (40 );V_ SQL varchar2 (100 );Cursor c_fk isSelect Sid, serial #From v $

Actions lov SHIFT + Ctrl + F8 Block menu Ctrl + B Clear block F7 Clear Field F5 Clear form F8 Clear record F6 Commit Ctrl + S Count query F12 Delete record Ctrl + up Display Error SHIFT + Ctrl + E Duplicate field SHIFT + F5 Duplicate record SHIFT +

Update operations on partition fields in a partitioned table By default,OraclePartition Table for partition field is not allowed to update operation, if there is a forward update to partition field, it will report an error -- ORA-14402: Update

The following SQL statement in PL/SQL: Select---- The root cause is clearly marked once, and every 4 RMB is a group of resources;Trunc (D. ITEM_ID-1)/1) + 1,-- Issue invoice, dateA. invoice_no,A. invoice_date,-- Keep others, keep RateA. currency,A.

The following functions must be implemented when creating an external table: The main invoice Table A has a customer named login Login A. IdentityThere is another table in Table B. There may be many partition methods for the same partition, or there

JAN-1(January) FEB-2(February) MAR-3(March)APR-4(April) MAY-5(May) JUN-6(June)JUL-7(July) AUG-8(August) SEP-9(September)OCT-10(October) NOV-11(November) DEC-12(December) **************************************** *************

Public void insertlog (string logview, string table_name, string table_cname){String SQL = "";Byte [] buffer = system. Text. encoding. Default. getbytes (logview );// SQL = "Update cap_log set log_text =: log_text where table_name =: table_name

Two different database servers read data from one user on one database server from another database server. In this case, you can use dblink. In fact, dblink is similar to the view in the database. When creating dblink, you need to know the IP

In many cases, you can use SQL tracking to diagnose the performance of a database and record some information in the trace file for further analysis. In general, we can set SQL tracking by initializing the parameter SQL _trace = true. We can also

Use of IF StatementsA. Basic if condition statements:Basic Syntax:Program code if then END IF; Example:Program code SQL> set serveroutput on; SQL> declare X number (3): = 9; Begin If x Dbms_output.put_line ('x is less than10 '); End

1. dbms_random.value Method Dbms_random is a package that can generate random values or strings. This package includes several functions, including initialize (), seed (), terminate (), value (), normal (), random (), and string (), but value () is

Today, I saw in a post that shiyiwan mentioned two concepts that I have never seen before: save exception and DML error logging. I searched the relevant content online and looked at it to understand the meaning, but I still did not use it in

First read the official Oracle explanationOracle managed file (OMF) A file that is created automatically by the Oracle database { Tagshow (event, 'server '); } "Href =" javascript:; "target =" _ Self "> ServerWhen it is needed and automatically

Use dbexportdoc V1.0 for Oracle to export the database table structure   Only download the tool and some basic usage steps are found on the Internet, but the specific usage of the tool is not described, the following describes how to use it based