Fortunately, Oracle provides you with theDUALtable which is a special table that belongs to the schema of the userSYSbut it is accessible to all users. TheDUALtable has one column namedDUMMYwhosedata typeisVARCHAR2()and contains one row with a valueX. ...
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SQL profile is a collection of additional statistical information stored in the data dictionary that helps the optimizer to generate the best plan for the query. SQL profile is managed through SQL_TUNE package of SQL tuning advisor. i.e when we run SQL tuning advisor against a query, The tun...
于是以“X$DUAL oracle”为关键词google了一下,找到Tom的一篇文章 1.What is the dual table, what is its purpose. dual is just a convienence table. You don't need to use it, you can use anything you want. The advantage to dual is the optimizer understands dual is a special one row, ...
NDB Cluster 8.0 is available as a General Availability (GA) release, beginning with NDB 8.0.19. NDB Cluster 7.6 and 7.5 are previous GA releases still supported in production; for information about NDB Cluster 7.6, see What is New in NDB Cluster 7.6. For similar information about NDB ...
dual是一个表,有一个名为DUMMY,类型为VARCHAR2(1)。DUMMY这个词在英文中的含义为“something designed to resemble and serve as a substitute for the real or usual thing; a counterfeit or sham.”,大概意思就是虚拟的,用来替代一些真实存在东西的概念。
name VARCHAR2(50), age NUMBER ); 上述代码创建了一个名为my_clob的CLOB类型的表格,包含了id、name和age三个列。 6. 总结 CLOB是Oracle数据库中一种用于存储以列为基础的数据的对象类型。它具有列级存储、灵活性高、可扩展性强和性能优越等特点,适用于数据量较大、需要频繁更新和需要查询特定列的场景。在使...
One column called DUMMY, which is of type VARCHAR2(1) One row with a value of ‘X’ Owned by the schema SYS So, it looks like this: DUMMY ‘X’ What’s The History of the DUAL Table and Why Is It Called DUAL? According toWikipedia, the DUAL table was created by Oracle staff me...
Varchar and Varchar2 are data types in databases for variable-length character strings; Varchar2 is more specific to Oracle with defined behavior for NULL and string length.
2. Functional programming to avoid local variables Simple is best, and there’s nothing wrong with using local variables. I wish I’d realised these facts when I wrote functions like this: FUNCTION address (i_name IN VARCHAR2 ,i_email_address IN VARCHAR2 ...