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21.Oracle - The self documenting dictionary

Oracle - The self documenting dictionary Oracle's Data dictionary is itself self documenting. we can query DICTIONARY AND DICT_COLUMNS views for descriptions of the data dictionary views and their columns. The following query gives the descriptions of all of the data dictionary views. SELECT table_name, comments FROM dictionary ORDER BY table_name; It gives the large amount of output. By using where class we can focus a smaller set of views as like the following query. SELECT table_name, comments FROM dictionary WHERE table_name LIKE '%TABLE%' ORDER BY table_name It returns all views containing the word 'TABLE' Like wise We can query the DICT_COLUMNS view also. It gives the descriptions for the columns for all views. Following query retrieves descriptions for the columns in ALL_TAB_COLUMNS. SELECT column_name, comments FROM dict_columns WHERE table_name = 'ALL_TAB_COLUMNS'; This is a sample one. We can learn lot about oracle through data d...
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20. TRIM Function

Which SELECT statement will the result 'elloworld' from the string 'HelloWorld'? A. SELECT SUBSTR( 'HelloWorld',1) FROM dual; B. SELECT INITCAP(TRIM ('HelloWorld', 1,1)) FROM dual; C. SELECT LOWER(SUBSTR('HellowWorld', 1, 1) FROM dual; D. SELECT LOWER(SUBSTR('HelloWorld', 2, 1) FROM dual; E. SELECT LOWER(TRIM ('H' FROM 'HelloWorld')) FROM dual; Answer: E Explanation: TRIM function accept a string describing the data you would like to trim from a column value. It can trim from both side of column value i.e. left and right. In the following statement this functionwill trim as SELECT LOWER(TRIM ('+' FROM 'HelloWorld')) FROM dual; From the above statement trim function will remove the character 'H' from 'HelloWorld' and LOWER function will convert the remaining character to lower case.
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19. Oracle Processes

Processes Oracle uses many small (focused) processes to manage and control the Oracle instance. This allows for optimum execution on multi-processor systems using multi-core and multi-threaded technology. Some of these processes include: PMON - Process Monitor SMON - System Monitor ARCn - Redo Log Archiver LGWR - Redo Log Writer DBWn - Database Writer CKPT - Checkpoint process RECO - Recoverer CJQn - Job Queue Coordinator QMNn - Queue-monitor processes Dnnn - Dispatcher Processes (multiplex server-processes on behalf of users) Snnn - Shared server processes (serve client-requests) MMAN - Internal process (used for internal database tasks) LSP0 - Logical standby coordinator process (controls Data Guard log-application) MRP - Media-recovery process (detached recovery-server process) MMON - Memory-monitor process MMNL - Memory monitor light (gathers and stores AWR statistics) PSP0 - Process-spawner (spawns Oracle processes) RFS - Remote file server process (archive to a remote site) DBRM ...
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18. ADDING CHECK CONSTRAINT WHILE INSERTING.

Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER NOT NULL EMP_NAME VARCHAR2(30) JOB_ID VARCHAR2(20) SAL NUMBER MGR_ID NUMBER DEPARTMENT_ID NUMBER You want to create a SQL script file that contains an INSERT statement. When the script is run, the INSERT statement should insert a row with the specified values into the EMPLOYEES table. The INSERT statement should pass values to the table columns as specified below: EMPLOYEE_ID: Next value from the sequence EMP_ID_SEQEMP_NAME and JOB_ID: As specified by the user during run time, through substitution variables SAL: 2000 MGR_ID: No value DEPARTMENT_ID: Supplied by the user during run time throughsubstitutionvariable. The INSERT statement should fail if the user supplies a value other than20 or 50. Which INSERT statement meets the above requirements? A. INSERT INTO employees VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL,&did); B. INSERT INTO employees VALUES (emp_id_seq.NEXTVAL, '...
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Question 16.Inserting more than 1 row/table with single query.

Can we insert more than 1 row with 1 qyery in same table/diff tables? Yes, we insert more than 1 row with 1 qyery by using the following method? syntax INSERT ALL INTO tablename1 (fieldlist) VALUES (valuelist) INTO tablename2 (fieldlist) VALUES (valuelist) INTO tablename3 (fieldlist) VALUES (valuelist) SELECT * FROM DUAL; Example: insert all into student (sno, name) values (1, 'Raja') into student (sno, name) values (2 'Ravi') into student (sno, name) values (3, 'Balu') select * from dual; We can use more than 1 table also. insert all into student (sno, name) values (1, 'Raja') into student (sno, name) values (2 'Ravi') into emp (eno, name) values (1, 'Mani') select * from dual; Interview quesitions and answers, objective type questions with answers : http://atchaya.com/ora/orahome.html Oracle forum : http://atchaya.wikidot.com/forum/c-91091/discussion-about-oracle
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Question 15

Write a PL/SQL Program for the following output --*-- -***- ***** -***- --*-- Answer The output based on the value of 'n' declare n number(2) default 20; i number(2); j number(2); h number(2); s number(2); b varchar2(1) default 'I'; begin s := 1; if n mod 2 = 0 then n := n+1; end if; h := n/2 -1; for i in 1..n loop for j in 1..h loop dbms_output.put('-'); end loop; for j in 1..s loop dbms_output.put('*'); end loop; for j in 1..h loop dbms_output.put('-'); end loop; dbms_output.put_line(' '); if n = s then b := 'D'; end if; IF b='I' then s := s+2; h := h-1; else s := s-2; h := h+1; end if; end loop; end;
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