Oracle

Subquery: A subquery When a query statement, he is nested in other SQL statements, the purpose is to provide data for the outer SQL statements, sub-queries can be used in DDL,DML,DQL.Using subqueries in DDL, you can quickly create a query-to-sum

Oracle Flashback Technologies-Flash back to the drop tableIn oracle10g, when a table is dropped, the table is not actually deleted, and the support is rename and placed in RecycleBin.#新建一个表y2, used to testSql> CREATE TABLE y2 as select * from

--View data usage for all table spacesSELECT Upper(f.tablespace_name) "tablespace name", D.TOT_GROOTTE_MB "table space size (M)", D.TOT_GROOTTE_MB-f.total_bytes "used Space (M)", To_char (Round((D.TOT_GROOTTE_MB-F.total_bytes)/D.tot_grootte_mb* -,2)

Stored procedures are used to perform specific operations when a stored procedure is established, you can specify either an input parameter (in) or an output parameter (out), you can pass the data to the execution part by using the input parameters

A single-line query is also called a single-line function that uses a function to manipulate data about a basic query:Oracle Basic Queries1Sql> Select lower (' Hello world ') Turn lowercase,2Upper (' Hello world ') to capitalize,3Initcap (' Hello

----Handle Deadlock processes--View locked tablesSelect B.owner,b.object_name,a.session_id,a.locked_modeFrom V$locked_object a,dba_objects bwhere b.object_id = a.object_id;--View the user who locked the tableSelect

NVL (commission_pct,0)If the first argument is null, the second argument is returnedIf the first argument is non-null, the first argument is returnedCOALESCE (EXPR1,EXPR2,EXPR3 ... EXPRn)A non-null value is returned when the first non-null value is

StringBuilder strSQL = new StringBuilder (); Strsql.append ("INSERT INTO YXZY_TSDQWH ("); Strsql.append ("TSDQ_SYB,TSDQ_DQ,TSDQ_LCLB)"); Strsql.append ("values"); Strsql.append ("@TSDQ_SYB, @TSDQ_DQ, @TSDQ_

ALTER DATABASE Character set Internal_use ZHS16GBK;ALTER DATABASE CHARACTER SET zhs16gbk;Oracle Modify character encoding 11 Opening a Command Window 22 View current character encoding 33 Executing the command 4Oracle Modified character encoding

:: Backup complete Empty database, including: table, view, sequence, function, package, etc.Exp aaa/[email PROTECTED]/ORCL owner=aaa file=f:\ccc.dmp rows=n statistics=none:: Back up a few table structures and dataExp Aaa/[email PROTECTED]/ORCL

database system: Microsoft's SQL Server, IBM DB2, Oracle of Oracle, MySQL, etc., are more well-known database management software. Now let's start with the Oracle database.Managing Oracle DatabasesOem:oracle Enterprise ManagerUsing graphical

http://blog.csdn.net/liangweiwei130/article/details/38223319 a very detailed description of the various storage typeshttp://www.jb51.net/article/74612.htm how cursor types are manipulatedHttps://www.2cto.com/database/201301/186608.html How to handle

Manage Oracle databases, from the simplest startup and shutdown databases.If Oracle is running under a Linux system, first of all, to connect to a Linux system,The SECURECRT is an ideal tool for connecting remote systems that run Windows, UNIX, and

Each database has a Alert_.log file, and the default storage path is $oracle_base/diag/rdbms///trace.A database alert file is a log file that lists messages in chronological order, such as: Any non-default initialization parameters used at

The goal of Oracle indexing is to avoid full table scans and improve query efficiency, but in some cases it is counterproductive.For example, there are millions data in a table, indexes a field, but there is no improvement in query performance,

1. Set the ID as a self-increment sequenceCREATE OR REPLACE TRIGGER "Datalib". " Trig_user_add "Before INSERT on ' Sys_user ' for each rowBeginSelect Seq_user.nextval into:new. " USER_ID "from dual;EndALTER TRIGGER "Datalib". " Trig_user_add "ENABLE;

Mysql> Select @rn: = @rn + 1 as rownum, Emp_no, Dept_no, From_date, To_date, from Dept_emp, (select @rn: = 0) A limit 20;+--------+--------+---------+------------+------------+| rownum | Emp_no | Dept_no | From_date | To_date |+--------+--------

Enter the parameter$in 1 = ' 2017-01-01 '; Must fill in$in 2 = ' 2017-08-01 '; Must fill in$in 3 = "; Optional fill $tns = ' (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = 0.0.0.0) (PORT = 1521)) (Connect_data = (service_name = dbname ) (SID =

Xiao Feng 91Subquery: When the result of one query is the condition of another query, that is, a SELECT statement embedded in another SQL statement becomes a nested query.A subquery can return a single row of results, can return multiple rows of

What is a tablespace?The Oracle database contains logical and physical structures.The physical structure of a database refers to a set of operating system files that make up a database.The logical structure of a database refers to a set of logical