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DDL Commands
TO CREATE TABLE.
SQL> create table depart(dno number(10),dname varchar2(10),primary key(dno));
Table created.
SQL> desc depart;
Name Null? Type
—————————————– ——– —————————-
DNO NOT NULL NUMBER(10)
DNAME VARCHAR2(10)
SQL> create table emp(eno number(10),ename varchar2(10),dno number(10),sal number(10),jobid varchar2(10),mgrid varchar2(10),foreign key(dno) references depart(dno));
Table created
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID VARCHAR2(10)
MGRID VARCHAR2(10)
TO ALTER THE TABLE
ADD
SQL> alter table emp add(primary key(eno),addr varchar2(10));
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID VARCHAR2(10)
MGRID VARCHAR2(10)
ADDR VARCHAR2(10)
SQL> alter table emp add(phno number(5));
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID CHAR(20)
MGRID VARCHAR2(10)
ADDR VARCHAR2(10)
PHNO NUMBER(5)
MODIFY
SQL> alter table emp modify(jobid char);
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID CHAR(20)
MGRID VARCHAR2(10)
ADDR VARCHAR2(10)
PHNO VARCHAR2(10)
SQL> alter table emp modify(jobid char(20));
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID CHAR(20)
MGRID VARCHAR2(10)
ADDR VARCHAR2(10)
PHNO VARCHAR2(10)
SQL> alter table emp modify(jobid char(5));
alter table emp modify(jobid char(5))
*
ERROR at line 1:
ORA-01441: cannot decrease column length because some value is too big
DROP
SQL> alter table emp drop(phno);
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID CHAR(20)
MGRID VARCHAR2(10)
ADDR VARCHAR2(10)
SQL> alter table emp drop(addr);
Table altered.
SQL> desc emp;
Name Null? Type
—————————————– ——– —————————-
ENO NOT NULL NUMBER(10)
ENAME VARCHAR2(10)
DNO NUMBER(10)
SAL NUMBER(10)
JOBID CHAR(20)
MGRID VARCHAR2(10)
TO DROP THE TABLE
SQL> drop table emp;
Table dropped.
SQL> desc emp;
ERROR:
ORA-04043: object emp does not exist