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create global temporary table myemp as select * from emp;
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alter table dept modify (Dname char(20));
alter table dept add (headcount number(3));
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create table emp3 as select * from emp;
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create table emp4 as select * from emp where rownum<1;
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alter table emp2 storage(next 256K pctincrease 0);
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alter table emp drop column comm;
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alter table emp move tablespace users;
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alter table emp set unused column xyz;
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create table worker
(  empno number(4) primary key,
   name  varchar2(10),
   age   number(2) check (age between 18 and 65),
   sex  char(2)  check (sex ='ÄÐ' or sex = ‘Å®’)
);