[وسط]Oracle Basic interview questions

1. What's the command to see the current user name?

Sql> show user;

2. What is the command to change the SQL prompt name?

SQL> set sqlprompt 'TYRO->'
TYRO-1 >

How do you switch to DOS prompt from SQL prompt?

SQL> host

How do I eliminate duplicate rows in an Oracle database?

DELETE FROM table_name WHERE ROWID NOT IN (SELECT   MAX (ROWID)
                             FROM table_name GROUP BY duplicate_values_field_name);

5. How do I display row number with records?
Use the row-num pseudocolumn with query, like

SQL> select rownum, ename from emp;

6. How do you display the records within a given range?SELECT ROWNUM, empno, ename

FROM emp WHERE ROWID IN (SELECT ROWID
                  FROM emp WHERE ROWNUM < = &rangeend
                MINUS
                SELECT ROWID
                  FROM emp WHERE ROWNUM < &rangebegin);

7. The NVL function only allows the same data type. But here's the task: if the commission field is null, then the text 'Not Applicable' should be displayed, instead of blank space. How do you write the query?

SQL> select nvl(to_char(comm.),'Not Applicable') from emp;

8. How do you view version information in Oracle?

SQL> select banner from $version;

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