oracle database 12c sql fundamentals

Oracle|sql server|access Database Tutorial All table names, field names SELECT * FROM user_tables WHERE table_name = ' username ' Use the following statement if you are logged on with this user:SELECT *From User_tables;If you are using another user:SELECT * from All_tables WHERE owner= ' user_name 'First, the first sentence: is the query of the user under all t

Sql%notfound is a Boolean value. Interacts with the most recent SQL statement (Update,insert,delete,select), which returns True when the most recent SQL statement does not involve any rows. Otherwise, false is returned. Such statements are useful in practical applications. For example, to update a row of data, if not found, you can do the appropriate action. Such

This article mainly introduces the PHP based on PDO database operation class, can achieve basic database connection, add and revise check, close connection and other operations, but also support for MySQL, SQL Server and Oracle database operations, the need for friends can r

A virtual index is a "false" index, which is defined in a data dictionary, but does not have the corresponding index segment, that is, it does not allocate any storage space. Using Virtual indexes, developersYou do not need to wait for the index to be created, or you do not need additional index storage space, you can use it as an index that already exists and test the execution plan of the SQL statement. If the optimizer isThe execution plan for

Database System class The teacher introduced 2 kinds of databases: Oracle database and SQL Server, also said the difference between their schema (schema, also known as architecture), here I also add with my common MySQL pattern differences, the memo. A pattern is equivalent to a namespace in a

ORACLE: Configure database connection // Database configuration file directoryE: \ oracle \ ora92 \ Network \ admin \ tnsnames. ora (Database name)Fwmsdb =(Description =(Address_list = Server IP Address(Address = (Protocol = TCP) (host = 10.10.6.40) (Port = 1521 )))(CONNECT_

I read ArticleHe talked about how to import data from SQL Server to the SQL Server compact edition database. What I need now is to replace SQL with an Oracle database, and my Oracle Da

Tags: des using os io file data ar ArtPL/SQL Connect Oracle Database 1, Brief introductionUse PL/SQL to connect to a remote Oracle database without installing an Oracle

Oracle Database PL/SQL process and function 4) process www.2cto.com 1. basic concept: oracle allows you to create and store compiled PL/SQL programs in the database, including processes, functions, packages, and triggers. We can s

Basic knowledge of oracle Database PL/SQL 1) Overview: the programming language formed by oracle procedural expansion in the standard SQL language is a unique feature of oracle, languages that support application development. Www.

In Oracle 10.2.0.4 database, there is a slow SQL execution, more than a few minutes without results, waiting for the event is idle Sql*net message events, and finally forced to break. This SQL is an ordinary UPDATE statement that has multiple tables associated in the WHERE

The database connection code provided in this article is an asp.net and Oracle, SQL Server, and Access database class. If you are an asp.net developer, you will be able to use it. net can be connected to Oracle, SQL Server, and Ac

Tags:. NET 127.0.0.1 Pictures Basic ext TNS TOC nbsp script1, first install Plsql client, Chinese, registration;2, download Oracle Client:instantclient-basic-nt-11.2.0.2.0.zip;3. Configuring the Plsql-tool-Connection Configuration Oracle home directory name path and OCI library path4. Configure oracle_home in the system environment variable5. Configure the E:\tools\instantclient_11_2\network\admin folder be

today, at dinner, my friend's database has a problem, CPU occupancy is 97%, when I see this problem, I think of the SQL is probably the cause of this problem, because can't help eating, temporarily did not help him to see this problem, this is my after-dinner simulation of the failure, carried out analysis:1) Check CPU process usage:See the Oracle process as 6331

----------------------------------------Why is that? Because subqueries are done on the index, and ordinary queries are done on a data file, the index file is generally much smaller than the data file, so it is more efficient to operate.You can actually use a similar strategy mode to deal with paging, such as judging if it is within 100 pages, using the most basic paging method, more than 100 pages, then use the sub-query paging method."Referencing the original, energy1010 space: MySQL paging

1. Types of SQL parse SQL parse is usually divided into hard parsing and soft parsing. When SQL is executed for the first time, hard parsing will occur, and subsequent execution will be soft parsing if it can be found in the shared pool. Therefore, to improve data performance, try to find the SQL statement executed eac

Oracle Database Programming: Develop PL/SQL subprograms and packages to develop PL/SQL subprograms and packages: subprograms: Compile rather than run at run time. Only calls can produce results. Subprograms are divided into store procedure and function, which are stored in the data