SQL Queries ask in Interviews Part 12

166)Display the department name along with total salary in each department.
SQL>select dname,sum(sal) from emp,dept where emp.deptno=dept.deptno group by dname;

167) Display itemname and total sales amount for each item.
SQL>select itemname,sum(amount) from item group by itemname;

168) Write a Query To Delete The Repeated Rows from emp table;
SQL>Delete from emp where rowid not in(select min(rowid)from emp group by ename);

169) TO DISPLAY 5 TO 7 ROWS FROM A TABLE
SQL>select ename from emp where rowid in(select rowid from emp where rownum<=7 minus select rowid from empi where rownum<5);

170)  DISPLAY  TOP N ROWS FROM TABLE?
SQL>SELECT * FROM
(SELECT *  FROM EMP ORDER BY ENAME DESC)
WHERE ROWNUM <10;

171) DISPLAY   TOP 3 SALARIES FROM EMP;
SQL>SELECT SAL FROM ( SELECT  * FROM EMP ORDER  BY SAL DESC ) WHERE ROWNUM <4;

172) DISPLAY  9th FROM THE EMP TABLE?
SQL>SELECT ENAME FROM EMP
WHERE ROWID=(SELECT ROWID FROM EMP WHERE ROWNUM<=10
MINUS
SELECT ROWID FROM EMP WHERE ROWNUM <10);

select second max salary from emp;
select max(sal) from emp where sal<(select  max(sal) from emp);

173) Delete the 10th record of emp table.
SQL>DELETE FROM EMP WHERE EMPNO=(SELECT EMPNO FROM EMP WHERE ROWNUM<11 MINUS
SELECT EMPNO FROM EMP WHERE ROWNUM<10);

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SQL Queries ask in Interviews Part 11

151) My boss has changed his mind.  Now he doesn’t want to pay more than 10,000.so revoke that salary constraint.
SQL>alter table emp modify constraint chk_001 enable;

152) Add column called as mgr to your emp table;
SQL>alter table emp add(mgr number(5));

153) Oh! This column should be related to empno.  Give a command to add this constraint.
SQL>ALTER TABLE EMP ADD CONSTRAINT MGR_DEPT FOREIGN KEY(MGR) REFERENCES EMP(EMPNO);

154) Add deptno column to your emp table;
SQL>alter table emp add(deptno number(5));

155) This deptno column should be related to deptno column of dept table;
SQL>alter table emp add constraint dept_001 foreign key(deptno) reference dept(deptno) [deptno should be primary key];

156) Give the command to add the constraint.
SQL>alter table <table_name) add constraint <constraint_name> <constraint type>;

157) Create table called as newemp.  Using single command create this table as well as get data into this table(use create table as);
SQL>create table newemp as select * from emp;
SQL>Create table called as newemp.  This table should contain only
empno,ename,dname.
SQL>create table newemp as select empno,ename,dname from emp,dept where
1=2;

158) Delete the rows of employees who are working in the company for more than 2 years.
SQL>delete from emp where (sysdate-hiredate)/365>2;

159) Provide a commission(10% Comm Of Sal) to employees who are not earning any commission.
SQL>select sal*0.1 from emp where comm is null;

160) If any employee has commission his commission should be incremented by 10% of his salary.
SQL>update emp set comm=sal*.1 where comm is not null;

161) Display employee name and department name for each employee.
SQL>select empno,dname from emp,dept where emp.deptno=dept.deptno;

162)Display employee number,name and location of the department in which he is working.
SQL>select empno,ename,loc,dname from emp,dept where emp.deptno=dept.deptno;

163) Display ename,dname even if there are no employees working in a particular department(use outer join).
SQL>select ename,dname from emp,dept where emp.deptno=dept.deptno(+);

164) Display employee name and his manager name.
SQL>select p.ename,e.ename from emp e,emp p where e.empno=p.mgr;

165) Display the department name and total number of employees in each department.
SQL>select dname,count(ename) from emp,dept where emp.deptno=dept.deptno group by dname;

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SQL Queries ask in Interviews Part 10

136) Display the 10th record of emp table without using group by and rowid?
SQL>SELECT * FROM EMP WHERE ROWNUM<11 MINUS SELECT * FROM EMP WHERE ROWNUM<10;

137) Create a copy of emp table;
SQL>create table new_table as select * from emp where 1=2;

138) Select ename if ename exists more than once.
SQL>select ename  from emp e group by ename having count(*)>1;

139) Display all enames in reverse order?(SMITH:HTIMS).
SQL>SELECT REVERSE(ENAME)FROM EMP;

140) Display those employee whose joining of month and grade is equal.
SQL>SELECT ENAME FROM EMP WHERE SAL BETWEEN
(SELECT LOSAL FROM SALGRADE WHERE
GRADE=TO_CHAR(HIREDATE,’MM’)) AND
(SELECT HISAL FROM SALGRADE WHERE
GRADE=TO_CHAR(HIREDATE,’MM’));

141) Display those employee whose joining DATE is available in deptno.
SQL>SELECT ENAME FROM EMP WHERE TO_CHAR(HIREDATE,’DD’)=DEPTNO;

142) Display those employees name as follows
A ALLEN
B BLAKE
SQL> SELECT SUBSTR(ENAME,1,1),ENAME FROM EMP;

143) List out the employees ename,sal,PF(20% OF SAL) from emp;
SQL>SELECT ENAME,SAL,SAL*.2 AS PF FROM EMP;

144) Create table emp with only one column empno;
SQL>Create table emp as select empno from emp where 1=2;

145) Add this column to emp table ename varchar2(20).
SQL>alter table emp add(ename varchar2(20));

146) Oops I forgot give the primary key constraint.  Add in now.
SQL>alter table emp add primary key(empno);

147) Now increase the length of ename column to 30 characters.
SQL>alter table emp modify(ename varchar2(30));

148) Add salary column to emp table.
SQL>alter table emp add(sal number(10));

149) I want to give a validation saying that salary cannot be greater 10,000 (note give a name to this constraint)
SQL>alter table emp add constraint chk_001 check(sal<=10000);

150) For the time being I have decided that I will not impose this validation.My boss has agreed to pay more than 10,000.
SQL>again alter the table or drop constraint with  alter table emp drop constraint chk_001 (or)Disable the constraint by using  alter table emp modify constraint chk_001 disable;

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SQL Queries ask in Interviews Part 9

121) Display those employee whose deptno is available in salary?
SQL>select emp.ename from emp, emp e where emp.sal=e.deptno;

122) Display those employee whose first 2 characters from hiredate -last 2 characters of salary?
SQL>select ename,SUBSTR(hiredate,1,2)||ENAME||substr(sal,-2,2) from emp;

123) Display those employee whose 10% of salary is equal to the year of joining?
SQL>select ename from emp where to_char(hiredate,’YY’)=sal*0.1;

124) Display those employee who are working in sales or research?
SQL>SELECT ENAME FROM EMP WHERE DEPTNO IN(SELECT DEPTNO FROM DEPT WHERE DNAME IN(‘SALES’,'RESEARCH’));

125) Display the grade of Akki?
SQL>SELECT ENAME,GRADE FROM EMP,SALGRADE WHERE SAL BETWEEN LOSAL AND HISAL AND Ename=’Akki’;

126) Display those employees who joined the company before 15 of the month?
SQL>select ename from emp where to_char(hiredate,’DD’)<15;

127) Display those employee who has joined before 15th of the month.
SQL>select ename from emp where to_char(hiredate,’DD’)<15;

128) Delete those records where no of employees in a particular department is less than 3.
SQL>delete from emp where deptno=(select deptno from emp group by deptno having count(deptno)<3);

129) Display the name of the department where no employee working.
SQL> SELECT E.ENAME,E.JOB,M.ENAME,M.JOB FROM EMP E,EMP M WHERE E.MGR=M.EMPNO;

130) Display those employees who are working as manager.
SQL>SELECT M.ENAME MANAGER FROM EMP M ,EMP E WHERE E.MGR=M.EMPNO GROUP BY M.ENAME;

131) Display those employees whose grade is equal to any number of sal but not equal to first number of sal?
SQL> SELECT ENAME,GRADE FROM EMP,SALGRADE WHERE GRADE NOT IN(SELECT SUBSTR(SAL,0,1)FROM EMP);

132) Print the details of all the employees who are Sub-ordinate to BLAKE?
SQL>select emp.ename from emp, emp e where emp.mgr=e.empno and e.ename=’BLAKE’;

133) Display employee name and his salary whose salary is greater than highest average of department number?
SQL>SELECT SAL FROM EMP WHERE SAL>(SELECT MAX(AVG(SAL)) FROM EMP GROUP BY DEPTNO);

134) Display the 10th record of emp table(without using rowid)
SQL>SELECT * FROM EMP WHERE ROWNUM<11 MINUS SELECT * FROM EMP WHERE ROWNUM<10;

135) Display the half of the ename’s in upper case and remaining lowercase?
SQL>SELECT SUBSTR(LOWER(ENAME),1,3)||SUBSTR(UPPER(ENAME),3,LENGTH(ENAME)) FROM EMP;

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SQL Queries ask in Interviews Part 8

106) Display name of those employee who are getting the highest salary?
SQL>select ename from emp where sal=(select max(sal) from emp);

107) Display those employee whose salary is equal to average of maximum and minimum?
SQL>select ename from emp where sal=(select max(sal)+min(sal)/2 from emp);

108) Select count of employee in each department  where count greater than 3?
SQL>select count(*) from emp group by deptno having count(deptno)>3;

109) Display dname where at least 3 are working and display only department name?
SQL>select distinct d.dname from dept d,emp e where d.deptno=e.deptno and 3>any (select count(deptno) from emp group by deptno);

110) Display name of those managers name whose salary is more than average salary of his company?
SQL>SELECT E.ENAME,EMP.ENAME FROM EMP,EMP E WHERE EMP.EMPNO=E.MGR AND E.SAL>(SELECT AVG(SAL) FROM EMP);

111)Display those managers name whose salary is more than average salary of his employee?
SQL>SELECT DISTINCT EMP.ENAME FROM EMP,EMP E WHERE
E.SAL <(SELECT AVG(EMP.SAL) FROM EMP
WHERE EMP.EMPNO=E.MGR GROUP BY EMP.ENAME) AND
EMP.EMPNO=E.MGR;

112) Display employee name,sal,comm and net pay for those employee whose net pay is greter than or equal to any other employee salary of the company?
SQL>select ename,sal,comm,sal+nvl(comm,0) as NetPay from emp where sal+nvl(comm,0) >any (select sal from emp);

113) Display all employees names with total sal of company with each employee name?
SQL>SELECT ENAME,(SELECT SUM(SAL)  FROM EMP) FROM EMP;

114) Find out last 5(least)earners of the company.?
SQL>SELECT DISTINCT SAL FROM EMP E WHERE
5>=(SELECT COUNT(DISTINCT SAL) FROM EMP A WHERE A.SAL<=E.SAL)
ORDER BY SAL DESC;

115) Find out the number of employees whose salary is greater than their manager salary?
SQL>SELECT E.ENAME FROM EMP ,EMP E WHERE EMP.EMPNO=E.MGR AND EMP.SAL<E.SAL;

116) Display those department where no employee working?
SQL>select dname from emp,dept where emp.deptno not in(emp.deptno);

117) Display those employee whose salary is ODD value?
SQL>select * from emp where sal<0;

118) Display those employee whose salary contains al least 3 digits?
SQL>select * from emp where length(sal)>=3;

119) Display those employee who joined in the company in the month of Dec?
SQL>select ename from emp where to_char(hiredate,’MON’)=’DEC’;

120) Display those employees whose name contains “A”?
SQL>select ename from emp where instr(ename,’A')>0;
or
SQL>select ename from emp where ename like(‘%A%’);

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SQL Queries ask in Interviews Part 3

31) Display the maximum salary being paid to CLERK.
SQL>select max(sal) from emp where job=’CLERK’;

32) Display the maximum salary being paid to depart number 20.
SQL>select max(sal) from emp where deptno=20;

33) Display the minimum salary being paid to any SALESMAN.
SQL>select min(sal) from emp where job=’SALESMAN’;

34) Display the average salary drawn by MANAGERS.
SQL>select avg(sal) from emp where job=’MANAGER’;

35) Display the total salary drawn by ANALYST working in depart number 40.
SQL>select sum(sal) from emp where job=’ANALYST’ and deptno=40;

36) Display the names of the employee in order of salary i.e the name of the employee earning lowest salary    should salary appear first.
SQL>select ename from emp order by sal;

37) Display the names of the employee in descending order of salary.
SQL>select ename from emp order by sal desc;

38) Display the names of the employee in order of employee name.
SQL>select ename from emp order by ename;

39) Display empno,ename,deptno,sal sort the output first base on name and within name by deptno and with in deptno by sal.
SQL>select empno,ename,deptno,sal from emp order by;

40) Display the name of the employee along with their annual salary(sal*12).The name of the employee earning highest annual salary should apper first.
SQL>select ename,sal*12 from emp order by sal desc;

41) Display name,salary,hra,pf,da,total salary for each employee. The output should be in the order of total salary,hra 15% of salary,da 10% of salary,pf 5% salary,total salary will be(salary+hra+da)-pf.
SQL>select ename,sal,sal/100*15 as hra,sal/100*5 as pf,sal/100*10 as da, sal+sal/100*15+sal/100*10-sal/100*5 as total from emp;

42) Display depart numbers and total number of employees working in each department.
SQL>select deptno,count(deptno)from emp group by deptno;

43) Display the various jobs and total number of employees within each job group.
SQL>select job,count(job)from emp group by job;

44) Display the depart numbers and total salary for each department.
SQL>select deptno,sum(sal) from emp group by deptno;

45) Display the depart numbers and max salary for each department.
SQL>select deptno,max(sal) from emp group by deptno;

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SQL Queries ask in Interviews Part 7

91) Display ename who are working in sales dept.

SQL>select ename from emp where deptno=(select deptno from dept where dname=’SALES’);

92) Display employee name,deptname,salary and comm for those sal in between 2000 to 5000 while location is Ahmedabad .
SQL>select ename,dname,sal,comm from emp,dept where sal  between 2000 and 5000 and loc=’AHMEDABAD’ and emp.deptno=dept.deptno;

93)Display those employees whose salary greater than his manager salary.
SQL>select p.ename from emp e,emp p where e.empno=p.mgr and p.sal>e.sal;

94) Display those employees who are working in the same dept where his manager is work.
SQL>select p.ename from emp e,emp p where e.empno=p.mgr and p.deptno=e.deptno;

95) Display those employees who are not working under any manager.
SQL>select ename from emp where mgr is null;

96) Display grade and employees name for the dept no 10 or 30 but grade is not 4 while joined the company before 31-dec-82.
SQL>select ename,grade from emp,salgrade where sal between losal and hisal and deptno     in(10,30) and grade<>4 and hiredate<’31-DEC-82′;

97) Update the salary of each employee by 10% increment who are not eligible for commission.
SQL>update emp set sal=sal+sal*10/100 where comm is null;

98) SELECT those employee who joined the company before 31-dec-82 while their dept location is new york or  Chicago.
SQL>SELECT EMPNO,ENAME,HIREDATE,DNAME,LOC FROM EMP,DEPT WHERE (EMP.DEPTNO=DEPT.DEPTNO)AND HIREDATE <’31-DEC-82′ AND DEPT.LOC IN(‘CHICAGO’,'NEW YORK’);

99) DISPLAY EMPLOYEE NAME,JOB,DEPARTMENT,LOCATION FOR ALL WHO ARE WORKING AS  MANAGER?
SQL>select ename,JOB,DNAME,LOCATION from emp,DEPT where mgr is not null;

100) DISPLAY THOSE EMPLOYEES WHOSE MANAGER NAME IS AKKI? –[AND ALSO DISPLAY THEIR MANAGER NAME]?
SQL> SELECT P.ENAME FROM EMP E, EMP P WHERE E.EMPNO=P.MGR AND E.ENAME=’AKKI’;

101) Display name and salary of ford if his salary is equal to hisal of his grade
SQL>select ename,sal,grade from emp,salgrade where sal between losal and hisal and ename =’FORD’ AND HISAL=SAL;

102) Display employee name,job,depart name ,manager name,his grade and make out an under department wise?
SQL>SELECT E.ENAME,E.JOB,DNAME,EMP.ENAME,GRADE FROM EMP,EMP E,SALGRADE,DEPT WHERE EMP.SAL BETWEEN LOSAL AND HISAL AND EMP.EMPNO=E.MGR AND EMP.DEPTNO=DEPT.DEPTNO ORDER BY DNAME;

103) List out all employees name,job,salary,grade and depart name for every one in the company  except ‘CLERK’.Sort on salary display the highest salary?
SQL>SELECT ENAME,JOB,DNAME,SAL,GRADE FROM EMP,SALGRADE,DEPT WHERE SAL BETWEEN LOSAL AND HISAL AND EMP.DEPTNO=DEPT.DEPTNO AND JOB NOT IN(‘CLERK’)ORDER BY SAL ASC;

104) Display the employee name,job and his manager.Display also employee who are without manager?
SQL>select e.ename,e.job,eMP.ename AS Manager from emp,emp e where emp.empno(+)=e.mgr;

105) Find out the top 5 earners of company?
SQL>SELECT DISTINCT SAL FROM EMP E WHERE 5>=(SELECT COUNT(DISTINCT SAL) FROM EMP A WHERE A.SAL>=E.SAL)ORDER BY SAL DESC;

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SQL Queries ask in Interviews Part 6

76) Display the following output for each row from emp table. A has joined the company on wednesday 13th August ninten nintey.
SQL>select ENAME||’ HAS JOINED THE COMPANY ON  ‘||to_char(HIREDATE,’day ddth Month  year’)   from EMP;

77) Find the date for nearest saturday after current date.
SQL>SELECT NEXT_DAY(SYSDATE,’SATURDAY’)FROM DUAL;

78) Display current time.
SQL>select to_char(sysdate,’hh:MM:ss’) from dual.
79) Display the date three months Before the current date.
SQL>select add_months(sysdate,3) from dual;

80) Display the common jobs from department number 10 and 20.
SQL>select job from emp where deptno=10 and job in(select job from emp where deptno=20);

81)Display the names of employees who earn a salary more than that of A or that of salary greater than   that of B.
SQL>select ename,sal from emp where sal> (select sal from emp where ename=’A')and sal> (select sal from emp where ename=’B');

81) Display the jobs found in department 10 and 20 Eliminate duplicate jobs.
SQL>select distinct(job) from emp where deptno=10 or deptno=20;

(or)

SQL>select distinct(job) from emp where deptno in(10,20);

82) Display the jobs which are unique to department 10.
SQL>select distinct(job) from emp where deptno=10;

83) Display the details of those who do not have any person working under them.
SQL>select e.ename from emp,emp e where emp.mgr=e.empno group by e.ename having count(*)=1;

84) Display the details of those employees who are in sales department and grade is 3.
SQL>select * from emp where deptno=(select deptno from dept where dname=’SALES’)and sal between(select losal from salgrade where grade=3)and (select hisal from salgrade where grade=3);

85) Display those who are not managers and who are managers any one.
i)display the managers names
SQL>select distinct(m.ename) from emp e,emp m where m.empno=e.mgr;
ii)display the who are not managers
SQL>select ename from emp where ename not in(select distinct(m.ename) from emp e,emp m where m.empno=e.mgr);

86) Display those employee whose name contains not less than 4 characters.
SQL>select ename from emp where length(ename)>4;

87) Display those department whose name start with “S” while the location name ends with “K”.
SQL>select dname from dept where dname like ‘S%’ and loc like ‘%K’;

88) Display those employees whose manager name is akash.
SQL>select p.ename from emp e,emp p where e.empno=p.mgr and e.ename=’Akash’;

89) Display those employees whose salary is more than 3000 after giving 20% increment.
SQL>select ename,sal from emp where (sal+sal*.2)>3000;

90) Display all employees while their dept names;
SQL>select ename,dname from emp,dept where emp.deptno=dept.deptno;

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How to copy Table data from one DB to another DB

Here we are using TOAD to  copy Table data from one DB (Instance) to another DB (Instance).
Step1: Go to Schema where your table data exists

Step2:  Go to the Describe Objects Window (Place your cursor on Table and click F4 button)

Click on Copy data to another schema.
Step3: Give the Destination Connection and Schema and click on Run button(Begin Copying Data). You should have same table name with the same columns in the destination schema.

 

Now check data in the destination schema.

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Bonus and Salgrade tables script in Oracle

Bonus:

create table bonus(
  ename varchar2(10),
  job   varchar2(9),
  sal   number,
  comm  number);

Salgrade:

create table salgrade(
  grade number,
  losal number,
  hisal number
);

Salgrade Table data:

insert into salgrade
values (1, 700, 1200);
insert into salgrade
values (2, 1201, 1400);
insert into salgrade
values (3, 1401, 2000);
insert into salgrade
values (4, 2001, 3000);
insert into salgrade
values (5, 3001, 9999);

Also read: EMP and DEPT tables script in Oracle

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EMP and DEPT tables script in Oracle

Dept:

create table dept(
  deptno number(2,0),
  dname  varchar2(14),
  loc    varchar2(13),
  constraint pk_dept primary key (deptno)
);

Emp:

create table emp(
  empno    number(4,0),
  ename    varchar2(10),
  job      varchar2(9),
  mgr      number(4,0),
  hiredate date,
  sal      number(7,2),
  comm     number(7,2),
  deptno   number(2,0),
  constraint pk_emp primary key (empno),
  constraint fk_deptno foreign key (deptno) references dept (deptno)
);

Dept Table data:

insert into dept
values(10, 'ACCOUNTING', 'NEW YORK');
insert into dept
values(20, 'RESEARCH', 'DALLAS');
insert into dept
values(30, 'SALES', 'CHICAGO');
insert into dept
values(40, 'OPERATIONS', 'BOSTON');

Emp Table data:

insert into emp
values(
 7839, 'KING', 'PRESIDENT', null,
 to_date('17-11-1981','dd-mm-yyyy'),
 5000, null, 10
);
insert into emp
values(
 7698, 'BLAKE', 'MANAGER', 7839,
 to_date('1-5-1981','dd-mm-yyyy'),
 2850, null, 30
);
insert into emp
values(
 7782, 'CLARK', 'MANAGER', 7839,
 to_date('9-6-1981','dd-mm-yyyy'),
 2450, null, 10
);
insert into emp
values(
 7566, 'JONES', 'MANAGER', 7839,
 to_date('2-4-1981','dd-mm-yyyy'),
 2975, null, 20
);
insert into emp
values(
 7788, 'SCOTT', 'ANALYST', 7566,
 to_date('13-JUL-87','dd-mm-rr') - 85,
 3000, null, 20
);
insert into emp
values(
 7902, 'FORD', 'ANALYST', 7566,
 to_date('3-12-1981','dd-mm-yyyy'),
 3000, null, 20
);
insert into emp
values(
 7369, 'SMITH', 'CLERK', 7902,
 to_date('17-12-1980','dd-mm-yyyy'),
 800, null, 20
);
insert into emp
values(
 7499, 'ALLEN', 'SALESMAN', 7698,
 to_date('20-2-1981','dd-mm-yyyy'),
 1600, 300, 30
);
insert into emp
values(
 7521, 'WARD', 'SALESMAN', 7698,
 to_date('22-2-1981','dd-mm-yyyy'),
 1250, 500, 30
);
insert into emp
values(
 7654, 'MARTIN', 'SALESMAN', 7698,
 to_date('28-9-1981','dd-mm-yyyy'),
 1250, 1400, 30
);
insert into emp
values(
 7844, 'TURNER', 'SALESMAN', 7698,
 to_date('8-9-1981','dd-mm-yyyy'),
 1500, 0, 30
);
insert into emp
values(
 7876, 'ADAMS', 'CLERK', 7788,
 to_date('13-JUL-87', 'dd-mm-rr') - 51,
 1100, null, 20
);
insert into emp
values(
 7900, 'JAMES', 'CLERK', 7698,
 to_date('3-12-1981','dd-mm-yyyy'),
 950, null, 30
);
insert into emp
values(
 7934, 'MILLER', 'CLERK', 7782,
 to_date('23-1-1982','dd-mm-yyyy'),
 1300, null, 10
);

commit; 

Also read:Bonus and Salgrade tables script in Oracle

 

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Enhancements in Oracle 12c Database Part4

ROW limiting for Top-N result queries

There are various indirect approaches/methods exist to fetch Top-N query results for top/bottom rows in the previous releases. In 12c, retrieving Top-N query results for top/bottom rows simplified and become straight forward with the new FETCH FIRST|NEXT|PERCENT clauses.

In order to retrieve top 10 salaries from EMP table, use the following new SQL statement:

SQL> SELECT eno,ename,sal FROM emp ORDER BY SAL DESC FETCH FIRST 10 ROWS ONLY;

The following example limits the fetch to 10 per cent from the top salaries in the EMP table:

SQL> SELECT eno,ename,sal FROM emp ORDER BY SAL DESC FETCH FIRST 10 PERCENT ROWS ONLY;

The following example offsets the first 5 rows and will display the next 5 rows from the table:

SQL> SELECT eno,ename,sal FROM emp ORDER BY SAL DESC OFFSET 5 ROWS FETCH NEXT 5 ROWS ONLY;

All these limits can be very well used within the PL/SQL block too.

BEGIN

SELECT sal BULK COLLECT INTO sal_v FROM EMP FETCH FIRST 100 ROWS ONLY;

END;

Top-N Restrictions:

• If you have a SELECT statement with FOR UPDATE, you can’t use it.

• If the query of the Materialized Views has this clause, then you can’t do an incremental refresh of

that MV

DEFAULT Values for Columns on Explicit NULL Insertion

The DEFAULT definition of a column can be extended to have the DEFAULT being applied for explicit 

NULL insertion. The DEFAULT clause has a new ON NULL clause, which instructs the database to assign a specified default column value when an INSERT statement attempts to assign a value that evaluates to NULL.

SQL> create table t5 (col1 number, col2 number default on null 0);

Table created.

SQL> desc t5

Name Null? Type

------ --------- -------- --

COL1 NUMBER

COL2 NOT NULL NUMBER

SQL> insert into t5 values (1, null);

SQL> insert into t5 values (2,2);

SQL> select * from t5;

COL1 COL2

-------- ---------

1 0

2 2 

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Enhancements in Oracle 12c Database Part3

Extended data types

In 12c, the data type VARCHAR2, NAVARCHAR2, and RAW size will support up to 32,767 bytes in contrast to 4,000 and 2,000 in the earlier releases. The extended character size will reduce the use of going for LOB data types,  whenever possible. In order to enable the extended character size, you will have to set the MAX_STRING_SIZE initialization database parameter to EXTENDED.

Generated as Identity/Sequence Replacement

You can now create a column with 'generated as identity' clause. Thats it. Doing this is equivalent to creating a separate sequence and doing a sequence.nextval for each row. This is another handy and a neat feature which will help developer community. This is also called No Sequence Auto Increment Primary Key.
Identity Column creation:

SQL> create table t6 (col1 number generated always as identity);

SQL> create table t7 (col1 number generated always as identity (start with 1000 increment by 10));

SQL> insert into t6 values (1);

insert into t6 values (1)
*
ERROR at line 1:
ORA-32795: cannot insert into a generated always identity column

SQL> create table t9 (col1 number, col2 number generated by default as identity);

SQL> insert into t9 values (9,9);

SQL> insert into t9 values (10,default);

SQL> insert into t9 (col1) values (11);

SQL> select * from t9;

COL1 COL2
---------- ----------
9 9
10 2
11 3

WITH clause improvements

In 12c, you can have faster running PL/SQL function/procedure in SQL, that are defined and declared within the WITH clause of SQL statements. The following examples demonstrate how to define and declare a procedure or  function within the WITH clause:

WITH
PROCEDURE|FUNCTION test1 (…)
BEGIN
 <logic>
END;
SELECT <referece_your_function|procedure_here> FROM table_name;

Although you can’t use the WITH clause directly in the PL/SQL unit, it can be referred through a dynamic SQL within that PL/SQL unit.  The with clause inline PLSQL feature will make it possible to create a procedure or function inside your select statement instead of having to create this in a package or function. Oracle also says that this will optimize the performance against having to call a schema procedure/function

An Example:

WITH
FUNCTION FUNC_ADD_ONE(p_num IN NUMBER
IS
BEGIN
RETURN p_num+1;
SELECT FUNC_ADD_ONE(1) FROM Dual;

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