Oracle

Transfer required:EXISTS specifies a subquery to detect the presence of a row. Syntax: EXISTS subqueryParameter: subquery is a restricted SELECT statement (the COMPUTE clause and the INTO keyword are not allowed).Result type: Boolean returns TRUE if

the integrity constraints of data are some constraints on the data description, and three types of integrity constraints can be found in the relational data model: Entity integrity, referential integrity, and user-defined integrity.

1. Merge function wm_concat (column)Wm_concat (column name), which separates the column values by the "," number and displays them as a row. If the column value is in Chinese, choose another way: Wm_concat (to_char (column name))For example, the

I. Oracle monitoring, database, startup and deactivation of Oracle servers Login with root: Switch user su–root/root operating system, generally only the root user has access to the Oracle database server installed in the operating system, and

After 9i, the internal component size of the SGA can be dynamically adjusted or automatically managed by the database, and when the memory size is set, the basic unit of allocation is granularity (granule) granule is a contiguous virtual memory,

D:\install\PLSQL\instantclient_11_2An error occurred while reinstalling Oracle 11g,plsql connection Oracle today:ORA-12154:TNS: Unable to resolve the specified connection identifier. On the internet a rough look, the error is more common, mainly is

1. Dataguard Primary and Standby switching1.1. Check if the current master repository has switching conditions On slave SelectSequence#,first_time,next_time,archived,applied fromV$archived_logwheresequence#=(Select Max(sequence#) fromV$

 in the process of doing the project, a page uses a similar example of the following SQL query data. For the sake of secrecy and ease of use, I replaced the table names and fields in the project with the system tables and fields in the ORACLE

Oracle Learning1. Create a constraint for the table :ALTER TABLE name ADD CONSTRAINT constraint name constraint contentDemo sample: Alter bable infos add constraint un_stunsme unique (stuname)//UNIQUE constraint;ALTER TABLE scores add constraint

Source of original article (http://blog.csdn.net/lichkui/article/details/4306299)The merge statement is a new syntax for merging the UPDATE and INSERT statements oracle9i. Through the merge statement, the other table is queried based on the join

Two date Type fields: Start_date,end_date, which calculates the time difference between these two dates (in days, hours, minutes, seconds, milliseconds, respectively):Days:ROUND (To_number (end_date-start_date))Hours:ROUND (To_number (end_date-start_

The SQL language is divided into four categories:Data Query Language DQL:The DQL basic structure of the data query language is a query block consisting of a SELECT clause, a FROM clause, a WHERE clause.Data Manipulation Language DML:DML is shorthand

There are many application projects, just start with MySQL database can basically achieve a variety of functional requirements, with the increase in application users, data volume increases, MySQL gradually appeared overwhelmed: the connection is

1. DataDefinition: A symbol that describes a thing. For example: text, audio, and video are data.2. DatabaseStorage of Data Warehouse, stored in the computer, in a certain format, can be shared for users.3, the development stage of the database1.

1. Primary library settings Dataguard related parameters1.1. Force the Primay Library to log in any stateSYS@userdata>SelectForce_logging fromv$Database; Force_log---------Nosys@userdata>Alter DatabaseForce logging;Databasealtered.

OracleTwo table associated batch updateOne of the table data method one (Recommended）： update table 2 set table 2. C = ( select B from Table 1 where table 1. A = table 2. A) where exists ( select 1 from table 1 where

I. What is a database audit? Database audit, is the activity of the database to do tracking records, mainly including database connection, SQL statement execution, database object access to these aspects of tracking records.   Second, the memory of

Resolve Oracle Database Ora-00054:resource busy and acquire with NOWAIT specified errorWhen I use the PL/SQL Developer client call stored procedure to find a halfway card machine and then force termination of PL/SQL developer, Oracle has been locked

Classification of database operation statements DDL: Database schema definition language, keyword: create DML: Data manipulation language, keywords: Insert, delete, update DCL: Database control Language, keyword: Grant, remove

Oracle RAC Archive settings need to be less simple than single-instance setup, with some details to be noticed during the open processArchive Open Ideas:1: See if the database is open for archiving2: Create a shared directory (archive must be placed