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Question 1 (In DBMS like Oracle) Which of the following allow null values ? A Unique Key or Primary Key ? Answer : Primary Key constraint does not allow null values to be inserted while it is legal in case of Unique key. Question 2 Considering an Oracle database as an example, can NULL values be used in arithmetic operations ? Explain your answer ? Answer : No, NULL value cannot be used in arithmetic operation. This is because a NULL just denotes an 'absence' of information rather than 'empty' or 'zero' value. Question 3 How you can delete a duplicate row from Unique key column? Answer : This necessity does not arise. First of all Unique key column will not allow duplicate rows to be inserted. Question 4 Tell any one advantage of using stored procedures in applications? Answer : Stored Procedures abstract complex SQL queries from application code. For example, a task involving multiple lines of complex SQL queries can be simpli...

Top Sql Aptitude Questions for Aptitude Some SQL Aptitude questions for Aptitude Preparations Q  Which  is  the  subset  of  SQL  commands  used  to  manipulate  Oracle  Database structures, including tables? Data Definition Language (DDL) Q  What operator performs pattern matching? LIKE operator Q  What operator tests column for the absence of data? IS NULL operator Q  Which command executes the contents of a specified file?    START <filename> or @<filename> Q  What is the parameter substitution symbol used with INSERT INTO command?    &amp; Q  Which command displays the SQL command in the SQL buffer, and then executes it?.    RUN Q.  What are the wildcards used for pattern matching?    _ for single character substitution and % for multi-character substitution Q  State true or false. EXISTS, SOME, ANY are operators in SQL.   ...

Question: 1) Create orreplace trigger trig_msg after update ordelete or insert on customer for each row Code: declare oper varchar2(10); begin if updating then DBMS_OUTPUT.PUT_LINE('UPDATING'); end if; if deleting then DBMS_OUTPUT.PUT_LINE('DELETING'); end if; if inserting then DBMS_OUTPUT.PUT_LINE('INSERTING'); end if; end; SQL> set serveroutput on; SQL> insert into customer values(1,'vish','delhi',500,'21-jan-2001'); INSERTING 1 row created. SQL> delete from customer where loanno = 1; DELETING 1 row deleted. Question 2) create or replace trigger trig_nodml after update orinsert or delete on loan for each row Code: declare m varchar2(15); begin if updating then RAISE_APPLICATION_ERROR(-20000,'NO UPDATE ALLOWED'); end if; if deleting then RAISE_APPLICATION_ERROR(-20000,'NO DELETING ALLOWED'); end if; if inserting then m:=TO_CHAR(sysdate,'DAY'); if (upper(m)<...

PRACTICAL NO. 1 Create tables as per following definitions. Deposit3 : Actno Cname Brname Amount Date SQL> create table deposit3 (actno number(5),cname varchar(20),brname varchar2(20),amount number(10,2),dt date); Table created. Branch3 : Brid Brname City Ins_date Update_date SQL> create table branch3 (brid varchar2(20), brname varchar2(20),city varchar2(20),insdate date,update_date date); Table created. Customer3 : Custid Cname City ins_date update_date SQL> create table customer3           (custid varchar2(20), cname varchar2(20),city varchar2(20),insdate date,update_date date); Table created. Borrow3 : loanno custname brname amount ins_date SQL> create table borrow3           (loanno number(10), custname varchar2(20),brname varchar2(20),amount number(10,2),insdate date); Table created. Describe all tables. SQL> desc depo...