Sunday, 26 August 2012

SQL Interview Questions and Answers Part3


SELECT COUNT(column_name)
FROM user_tab_columns
WHERE table_name = 'MYTABLE';


dbms_output.enable(4000);  /*allows the output buffer to be increased to the specified number of bytes */


DECLARE
BEGIN
dbms_output.enable(4000);
FOR i IN 1..400
LOOP
DBMS_OUTPUT.PUT_LINE(i);
END LOOP;
END;
/


Set the following to some other character. By default it is &.

set define '~'

44.  How do you remove Trailing blanks in a spooled file :
Change the Environment Options Like this :
set trimspool on
set trimout on


Sample :1
CREATE OR REPLACE PROCEDURE CNT(P_TABLE_NAME IN VARCHAR2)
AS
SqlString VARCHAR2(200);
tot number;
BEGIN
SqlString:='SELECT COUNT(*) FROM '||  P_TABLE_NAME;
EXECUTE IMMEDIATE SqlString INTO tot;
DBMS_OUTPUT.PUT_LINE('Total No.Of Records In ' || P_TABLE_NAME || ' ARE=' || tot);
END;

Sample :2
DECLARE
            sql_stmt VARCHAR2(200);
            plsql_block VARCHAR2(500);
            emp_id NUMBER(4) := 7566;
            salary NUMBER(7,2);
            dept_id NUMBER(2) := 50;
            dept_name VARCHAR2(14) := ’PERSONNEL’;
            location VARCHAR2(13) := ’DALLAS’;
            emp_rec emp%ROWTYPE;
BEGIN
            EXECUTE IMMEDIATE 'CREATE TABLE bonus (id NUMBER, amt NUMBER)';

            sql_stmt := 'INSERT INTO dept VALUES (:1, :2, :3)';
            EXECUTE IMMEDIATE sql_stmt USING dept_id, dept_name, location;

            sql_stmt := 'SELECT * FROM emp WHERE empno = :id';
            EXECUTE IMMEDIATE sql_stmt INTO emp_rec USING emp_id;

            plsql_block := 'BEGIN emp_pkg.raise_salary(:id, :amt); END;';
            EXECUTE IMMEDIATE plsql_block USING 7788, 500;

            sql_stmt := 'UPDATE emp SET sal = 2000 WHERE empno = :1
            RETURNING sal INTO :2';
            EXECUTE IMMEDIATE sql_stmt USING emp_id RETURNING INTO salary;

            EXECUTE IMMEDIATE 'DELETE FROM dept WHERE deptno = :num'
            USING dept_id;

            EXECUTE IMMEDIATE ’ALTER SESSION SET SQL_TRACE TRUE’;
END;

Sample 3
CREATE OR REPLACE PROCEDURE DEPARTMENTS(NO IN DEPT.DEPTNO%TYPE) AS
              v_cursor integer;
              v_dname  char(20);
              v_rows   integer;
            BEGIN
              v_cursor := DBMS_SQL.OPEN_CURSOR;
              DBMS_SQL.PARSE(v_cursor, 'select dname from dept where deptno > :x', DBMS_SQL.V7);
              DBMS_SQL.BIND_VARIABLE(v_cursor, ':x', no);
              DBMS_SQL.DEFINE_COLUMN_CHAR(v_cursor, 1, v_dname, 20);
              v_rows := DBMS_SQL.EXECUTE(v_cursor);
              LOOP
                IF DBMS_SQL.FETCH_ROWS(v_cursor) = 0 THEN
                   EXIT;
                END IF;
                DBMS_SQL.COLUMN_VALUE_CHAR(v_cursor, 1, v_dname);
                DBMS_OUTPUT.PUT_LINE('Deptartment name: '||v_dname);
              END LOOP;
              DBMS_SQL.CLOSE_CURSOR(v_cursor);
            EXCEPTION
              WHEN OTHERS THEN
                   DBMS_SQL.CLOSE_CURSOR(v_cursor);
                   raise_application_error(-20000, 'Unknown Exception Raised: '||sqlcode||' '||sqlerrm);
END;


Difference 1:
            Oracle : select name from table1 where name like 'k%';
            Access: select name from table1 where name like 'k*';
Difference 2:
            Access: SELECT  TOP 2 name FROM Table1;
            Oracle : will not work there is no such TOP key word.


SELECT organization_id,name
FROM hr_all_organization_units
WHERE organization_id in
(
SELECT ORGANIZATION_ID_CHILD FROM  PER_ORG_STRUCTURE_ELEMENTS
CONNECT BY PRIOR
ORGANIZATION_ID_CHILD = ORGANIZATION_ID_PARENT
START WITH
ORGANIZATION_ID_CHILD = (SELECT organization_id
FROM hr_all_organization_units
WHERE name =  'EBG Corporate Group'));


CREATE OR REPLACE PROCEDURE read_data
AS
c_path             varchar2(100) := '/usr/tmp';
c_file_name     varchar2(20)  := 'EKGSEP01.CSV';
v_file_id           utl_file.file_type;
v_buffer           varchar2(1022) := This is a sample text’;
BEGIN
v_file_id := UTL_FILE.FOPEN(c_path,c_file_name,'w');
UTL_FILE.PUT_LINE(v_file_id, v_buffer);
UTL_FILE.FCLOSE(v_file_id);

v_file_id := UTL_FILE.FOPEN(c_path,c_file_name,'r');
UTL_FILE.GET_LINE(v_file_id, v_buffer);
DBMS_OUTPUT.PUT_LINE(v_buffer);
UTL_FILE.FCLOSE(v_file_id);
END;
/


SELECT DBMS_RANDOM.VALUE (1,2) FROM DUAL;


SELECT
       FLOOR((date1-date2)*24*60*60)/3600)
       || ' HOURS ' ||
       FLOOR((((date1-date2)*24*60*60) -
       FLOOR(((date1-date2)*24*60*60)/3600)*3600)/60)
       || ' MINUTES ' ||
       ROUND((((date1-date2)*24*60*60) -
       FLOOR(((date1-date2)*24*60*60)/3600)*3600 -
       (FLOOR((((date1-date2)*24*60*60) -
       FLOOR(((date1-date2)*24*60*60)/3600)*3600)/60)*60)))
       || ' SECS ' time_difference
FROM   my_table;


I have this string in a column named location

LOT 8 CONC3 RR

Using instr and substr, I want to take whatever value follows LOT and put
it into a different column and whatever value follows CONC and put it into
a different column


select substr('LOT 8 CONC3 RR',4,instr('LOT 8 CONC3 RR','CONC')-4) from
dual;

select substr('LOT 8 CONC3 RR',-(length('LOT 8 CONC3 RR')-(instr('LOT 8
CONC3 RR','CONC')+3)))
from dual


select text from all_source where name = 'X'
order by line;
select text from user_source where name = 'X'
select text from user_source where type = 'procedure' and
name='procedure_name';
select name,text from dba_source where name='ur_procedure'
and owner='scott';


select  to_number('-999,999.99', 's999,999.99')  from dual;               -999,999.99
select  to_number('+0,123.45', 's999,999,999.99')  from dual;           123.45
select  to_number('+999,999.99', 's999,999.99')  from dual;  999,999.99


select column_name from user_tab_columns where TABLE_NAME = 'EMP'
select column_name from all_tab_columns where TABLE_NAME = 'EMP'
select column_name from dba_tab_columns where TABLE_NAME = 'EMP'
select column_name from cols where TABLE_NAME = 'EMP'

I have a table have
a,b,c field,

a,b should be unique, and leave max(c) row in.
How can I delete other rows?

delete from 'table'
where (a,b,c)  not in (select a,b,max(c) from 'table' group by a,b);

56. CLOB to Char                              

1)  This function helps if your clob column value not exceed 4000 bytes
(varchar2 limit).if clob column's data exceeds 4000 limit, you have to
follow different approach.

 create or replace function lob_to_char(clob_col clob) return varchar2 IS
 buffer  varchar2(4000);
 amt                 BINARY_INTEGER := 4000;
 pos                  INTEGER := 1;
 l   clob;
 bfils    bfile;
 l_var   varchar2(4000):='';
 begin
  LOOP
              if dbms_lob.getlength(clob_col)<=4000 THEN
                            dbms_lob.read (clob_col, amt, pos, buffer);
                           l_var := l_var||buffer;
                           pos:=pos+amt;
              ELSE
                 l_var:= 'Cannot convert to varchar2..Exceeding varchar2 field
limit';
/
                   exit;
     END IF;
  END LOOP;
 return l_var;
 EXCEPTION
             WHEN NO_DATA_FOUND THEN
   return l_var;
 END;


2) CREATE GLOBAL TEMPORARY TABLE temp_tab(id number,varchar_col
varchar2(4000));

SQL> var r refcursor
SQL> exec lobpkg.lob_to_char(:r);
SQL> print r

create or replace package lobpkg is
type ref1 is ref cursor;
n number:=0;
PROCEDURE lob_to_char(rvar IN OUT lobpkg.ref1) ;
end;
/

create or replace package body lobpkg is

PROCEDURE lob_to_char(rvar IN OUT lobpkg.ref1) IS
buffer               varchar2(4000);
amt             BINARY_INTEGER := 4000;
pos              INTEGER := 1;
l                       clob;
r lobpkg.ref1;
bfils                 bfile;
l_var                varchar2(4000):='';
CURSOR C1 IS SELECT * FROM clob_tab;
-- change clob_tab to your_table_name
begin
n:=n+1;
FOR crec IN c1 LOOP
amt:=4000;
pos:=1;
BEGIN
            LOOP

--change crec.clob_col to crec.your_column_name

                                    dbms_lob.read (crec.clob_col, amt, pos, buffer);

--change next line if you create temporary table with different name

                                    insert into temp_tab values (n,buffer);

                                    pos:=pos+amt;
 
                       
            END LOOP;
EXCEPTION
            WHEN NO_DATA_FOUND THEN
                        NULL;
END;
END LOOP;
--change next line if you create temporary table with different name
open rvar for select vchar from temp_tab where id=n;
                       
END;
END;

57. Change Settings

Open file oracle_home\plus32\glogin.sql and
add this
set linesize 100
set pagewidth 20
and save the file
and exit from sql and reload then it will set it.


 declare
  -- we need one here to get a single quote into the variable
 v_str varchar2 (20) := 'O''reilly''s';
 begin
   DBMS_OUTPUT.PUT_LINE ( 'original single quoted v_str= ' || v_str );
   v_str := replace(v_str, '''', '''''');
   DBMS_OUTPUT.PUT_LINE ( 'after double quoted v_str= ' || v_str );
 end;
SQL> /
original single quoted v_str= O'reilly's
after double quoted v_str= O''reilly''s


CREATE OR REPLACE FUNCTION to_hms (i_days IN number)
   RETURN varchar2
IS
BEGIN
   RETURN TO_CHAR (TRUNC (i_days)) &#124&#124 ' days ' &#124&#124
                         TO_CHAR (TRUNC (SYSDATE) + MOD (i_days, 1), 'HH24:MI:SS');
END to_hms;

select to_hms(to_date('17-Jan-2002 13:20:20', 'dd-Mon-yyyy hh24:mi:ss') -
       to_date('11-Jan-2002 11:05:05', 'dd-Mon-yyyy hh24:mi:ss')) from
dual;

The table in both the schemas should have exactly the same structure. The data in
it could be same or different

a-b and b-a

select *   from a.a minus  select *  from b.a  and  select *   from b.a minus select *   from a.a


select * from user_jobs;
exec dbms_job.remove(job_no);

62. Switching Columns
Update tblname
Set  column1 = column2,
      Column2 = column1;

I have the number e.g. 63,9823874012983 and I want to round it to 63,98 and at the same time change the , to a .

select round(replace('63,9823874012983',',','.'),2) from dual;

64. First date of the year
select trunc(sysdate, 'y') from dual;

01-jan-2002

last year this month through a select statement
select add_months(sysdate, -12) from dual;
05-APR-01

65. Create Sequence
create sequence sh increment by 1 start with 0;

66. Cursors
cursor is someting like pointers in C language.
u fetch the data using cursor.( wiz...store it somewhere temporarily). u
can do any manipulation to the data that is fetched by the cursor. like
trim, padd, concat or validate. all this are done in temporary areas called
as context area or the cursor area. u can insert this data again in some
other table or do anything u want!!...like setting up some flags etc.
U can display the contents of cursor using the dbms_output only. U can
create an anonymous plsql block or a stored procedure. the major advantage
of cursors is that you can fetch more thatn one row and u can loop through
the resultset and do the manupulations in a secure manner.

set serveroutput on;
declare
cursor c1 is select * from emp;
begin
for var in c1 loop
exit when c1%notfound;
dbms_output.put_line('the employee' &#124&#124 var.ename &#124&#124'draws a
salary of '&#124&#124 var.sal);
end loop;
end;


select next_day(sysdate-7,'SUNDAY'), next_day(sysdate,'SATURDAY') from dual;

NEXT_DAY( NEXT_DAY(
--------- ---------
07-APR-02 13-APR-02

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