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alter table tb_test modify permile number(5,2);
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alter table tb_test add permile_temp number(5,2)
update tb_test set permile_temp=permile;
alter table drop column permile;
alter table test rename column permile_temp to permile;
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alter table tb_test add permile_temp number;
Add/modify columns
alter table tb_test modify PERMILE null;
update tb_test set permile_temp=permile,permile=null;
commit;
alter table tb_test modify permile number(5,2);
update tb_test set permile=permile_temp,permile_temp=null;
commit;
alter table tb_test drop column permile_temp;
alter table tb_test modify PERMILE not null;
select * from tb_test ;
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A schema is a collection of database objects (used by a user.).
Schema objects are the logical structures that directly refer to the database’s data.
A user is a name defined in the database that can connect to and access objects.
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