FREQENTLY ASKED QUESTIONS

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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 vrachar2(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.

Again alter the table or drop constraint with alter table emp drop constraint chk_001 (or)Disable the constraint by using

SQL>alter table emp modify constraint chk_001 disable;

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