Oracle

first, create a table space1. Set the instance nameEcho $ORACLE _sidExport Oracle_sid=mvbpbang2, sqlplus login/sqlplus Command LoginWhen you install Oracle, you need to remember the set global database name (default = ORCL) and password when you log

Expression: NVL (filed, replace)The function of the NVL function is that the value of the field that is encountered in the query is NULL, replace NULL with replace, and change its null query value.NVL can convert any data type, but only if the type

Oracle Lock table is relatively simple, the session of the query lock table can be killed.1, the following are related to the tableSELECT * fromV$lock;SELECT * fromV$sqlarea;SELECT * fromv$session;SELECT * fromv$process;SELECT *

I. Overview　Other database objects　　　　The main mastery is the sequenceSecond, sequence　1. What is a sequence　　Sequence: A database object that can be used by multiple users to produce unique valuesAutomatically provide a unique valueShared objects　　　

A study think three knocks to understand, can long-term effective memoryWhen I first learned Oracle, we learned about Oracle's advantages, such as distributed management, easy coordination, superior performance, support for big data formats, and the

first, the use of SQL developer　　Login　　Log in as a Scott User:　　　　Login page:　　　　Import Table:　　. Place the imported table in any location: (Select the D packing directory here)　　　Execute the following command: order needs to be consistent!　　　　　　　　

Create or Replace procedurePrc_table_count (P_flag outvarchar2) asTCOUNT Number; Scount Number; CountsqlVARCHAR2( -);BEGINTCOUNT:= 0; Scount:= 0; forC_rowinch ( Selecttable_name fromSYS. User_tab_comments TWHERET.table_name like 'zzjg%') LOOP

Actually length and vsize these twofunctionThe connection is not big, the difference is great. Although it is all "fetch length", but lengthfunctionThe result is "how many characters", vsize The result is "how many bytes are needed".Simply look at

Test forms using the Oracle database:--single-Table query data Syntax Select (query) * All/query fields, multiple fields, separating from table name--find information for all employeesSelect * fromscott.emp;Select * fromDept;--query all employee

--View tablespace names, path, size, and usage of data filesSelect B.tablespace_name "tablespace name",B.file_name "Data file path",b.bytes/1024/1024 "Size (M)",SUBSTR ((B.bytes-sum (NVL (a.bytes,0))/(b.bytes) *100,1,5) "Utilization"From

1 Status queries Start state SQL Statement Results Nomount Select status from V$instance; STARTED Select Open_mode from V$database; ERROR at line 1:Ora-01507:database not mounted

Oracle index and oracle index IndexIs a schema object that contains entries of each value. This entry appears in the index column of a table or cluster and provides direct and fast access to rows. Create an index: create index name on table name

Oracle procedure encryption method, oracle encryption procedure Oracle object Encryption Method I. wrap Encryption The following is a test procedure: [Oracle @ orclrac1:/home/oracle] $ cat sp_test. SQL Create or replace procedure leo (I in

Oracle filters repeated records of a field and obtains only one record. The oracle Field I. First thought: 1. Keyword distinct 2, group A function such as 3, MAX, and MIN is called a clustering function, which is used together with a GROUP. But none

Step-by-Step tutorial on deploying an Oracle database with tar: deploy an oracle database with tar There is a project on hand that may require downtime and maintenance, and it is likely that the host fails to be started. In case of a temporary

The problem of flute product in SQL and multi-table join operations, SQL flute (Scott account)   SELECT * FROM scott. dept; -- 4SELECT * FROM scott. emp; -- 14 /**Cartesian ProductInternal Connection (equivalent connection)External Connection

Oracle database instances and servicesA. instances and databases 1. instance: A group of Oracle background processes/threads andShared Memory ZoneThe memory is shared by threads/processes running on the same computer. An instance is used to manage

Specification for optimizing oracle SQL statements and compiling oraclesql statements 1. In principle, the partition key must be used as a condition for partition table queries; 2. Disable the use of functions in the left column of the WHERE clause,

Detailed description of oracle table preparation, index testing, SQL query execution times, And tablespace creation methods. oraclesql Put a system diagram first, Table preparation Create table t as select * from all_objects;Index test Create

Summary of Oracle details, oracle details Database creation and managementI. database creation problems:Data is organized in the form of a two-dimensional table. A table consists of columns and rows. A Row corresponds to an entity instance, which