Oracle

1, from the top down queryUse start with a= ' starting ID ' connect by prior a= BA is a subkey and B is the parent.Select F_ca_code,f_ca_parentcode,level from with='0' by=Query Result:Where level is the Oracle built-in functionIf you join a query,

Oracle "CONNECT by" is a hierarchical query clause that is typically used for queries of tree or hierarchical result sets. Its syntax is: [ START WITHcondition ] CONNECTBY[ NOCYCLE ] condition Description1. Start with: Tells the system which node to

I. Transactions and stored ProceduresHow transactions are used in a stored procedure. When you need to execute multiple additions, modifications, and deletions of SQL statements in a stored procedure, we need to use transactions to ensure data

SELECT from WHERE = and = ?The problem arises:Today's production Code performance scan This script is pulled out, because this thing is too long execution time, the back of the Code brothers are blocked, and then found that the guy is doing a full

1. Eliminate duplicate rowsIn the results of an Oracle query, there may be several rows in the same situation, so you can use distinct to eliminate duplicate rows.Code Demo: Distinct eliminate duplicate rows2. Null operationIf there is a missing

Oracle MySql[Java] Driver&url for Oracle and MySQL

In the previous blog examples, we created a function-based index, but if you execute the following query:select * from EMP where substr (ename,1,1) = ' S ';The resulting execution plan will still be (TABLE ACCESS full) because the function-based

These articles of Oracle Performance optimization operations can be used in conjunction with each other. And the various methods of interaction, close contact.This connection is both consistent and may bring conflict, when the conflict occurs, the

One, a stored procedure with a cursor　　There are two types of cursors as arguments:　　1. Declaring the system cursor type Sys_refcursor1) The cursor acts as a parameter to the stored procedure:--stored procedures with cursorsCREATE OR REPLACE

One. The SQL language supports the following categories of commands1. Data definition Language (DDL): Create, Alter (change), and drop (delete) commands1.1 Create (creating tables, table spaces, users, indexes, views, synonyms, procedures,

DBA training content notes and dba training content notes014-12-23slow hang lock: three common performance problems: hang. The whole database does not respond and new connections cannot be created. hanganalyze output. whether the dump file has

Table Partitioning (learning notes), Table Partitioning learning notes Table partition: Application Scenario: For tables with a large data volume, for example, tables with 2 GB of data, 20 pieces can be queried, which is certainly faster than

OracleDML Error Log DML error log is an error log function introduced by oracle10gR2 similar to SQL * Loader. The basic principle is to transfer any records that may cause statement failure to an error log table. The specific usage is as follows: 1.

Create and call functions and stored FunctionsFunction [in out parameter] -- Function [in out parameter] create or replace function get_test (m_id in number, str1 out varchar2) -- The parameter does not need type length return varchar2 is str2

Common Oracle functions-character and mathematical functions Various functions are often used in the development and use of oracle. This chapter summarizes simple strings and mathematical functions, which will be convenient to use in the future, it

Oracle performance optimization operations: Summary These articles about oracle performance optimization can be used in combination with each other. In addition, various methods are closely related to each other. This kind of connection is

Oracle performance optimization operation 18: whether to use full table scan or index Like all tips, the last trick will go back to the starting point. Finally, let's discuss whether to create an index, maybe it is faster to perform a full table

Package (study notes) and study notes Example 1,Locate all employees in the department according to the entered Department number. First, create a package and define the package specifications. Create or replace package getemp_pkg is FUNCTION

Oracle11gRMAN: ActiveDatabaseDuplicationforstandbydatabaseIf the production-based duplicate replication is not manually configured with pfile (set memory, process, dg-related configuration parameters, database-related path parameters), various

Oracle System Toolkit (Study Notes), oracle Study Notes Dbms_Output package   No. Subroutine name Description 1 Enable Open the buffer, when the user usesThis statement is automatically called when the "set serveroutput