Oracle dual table and oracledual table

Oracle dual table and oracledual table

A Dual table is generated by default when each database is created. The table has only one column and one row.

1) analyze the dual table as follows:

 

2) application:

In the oracle database, the dual table exists as a virtual table, because the oracle query operation statement must meet the format: select columnname from tablename, where the from point must represent, therefore, some non-query operations can be implemented through dual tables, such:

-- View the current date:

Select sysdate from dual;

 

 

-- Calculation equations:

Select 3*3-3 as result, 8-9 as plus from dual;

 

 

-- Concatenate a string:

Select 'this' | 'is '| 'test' from dual;

 

 

-- Execute other operations without specific tables

 

 

 

 

 

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This series is a learning note for oracle recently. It is recorded here as a review of itself. Some of them come from the Internet, some come from books, but it has been a long time and cannot be remembered which are references, if it is reprinted but not marked, we apologize.