还有一个叫DUAL的public synonym,所以任意的用户都可以访问到DUAL了。 神奇的是,DUAL这货在实例是nomount的状态下也可以访问: [oracle@bogon~]$ sqlplus/assysdbaSQL*Plus:Release12.1.0.2.0ProductiononWedDec1008:00:152014Copyright (c)1982,2014, Oracle.Allrights reserved. Connectedtoan idle instance.SQL>sta...
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, one column table -- when you use it in queries, it uses thi...
Now, this is only Oracle-specific. If you’ve used SQL Server or MySQL, you don’t need to specify a DUAL table. What Columns Can I Select? I mentioned earlier that the DUAL table is a dummy table used for functions and calculations in your queries. Normally, when you run a SELECT ...
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EXEC DBMS_SQLTUNE.execute_tuning_task(task_name => '5dkrnbx1z8gcb_tuning_task_1'); SET LONG 10000000; SET PAGESIZE 100000000 SET LINESIZE 200 SELECT DBMS_SQLTUNE.report_tuning_task('5dkrnbx1z8gcb_tuning_task_1') AS recommendations FROM dual; ...
The most common strong authentication policy is dual-factor authentication. When logging in to the system, a user needs to provide not only the user name and password, but also the items bound to the user name and password (for example, USB keys are widely used in online banking), or ...
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Introduction to the Oracle dual table# In Oracle, theSELECTstatement must have aFROMclause. However, some queries don’t require any table, for example: SELECTUPPER('This is a string')FROMwhat_table;Code language:SQL (Structured Query Language)(sql) ...
“Unable to enlist in the transaction” with Oracle linked server from MS SQL Server [<Name of Missing Index, sysname,>] in non clustered index [Execute SQL Task] Error: The value type (__ComObject) can only be converted to variables of type Object. [ODBC Driver Manager] Data source nam...
Re: why does "select 1 from dual" work - what is the "1"? Hi,this is all explained in the documentation :"DUAL is a table automatically created by Oracle Database along with the data dictionary. DUAL is in the schema of the user SYS but is accessible...