Oracle field (primary key) type modification method for processing existing data

2. From me Oracle Latest SQL Recall Walkthrough 11 blog post http://blog.csdn.net/luozhonghua2014/article/details/45729669
4. Just re-publish once, is to extract experience, so that we can find a solution
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   --------Modify the field type of the existing data (the first 4 steps will cause the constraint in the table to be lost)  --1 rename field  ALTER TABLE example rename column ID to Sid;  --2 Add ID field  ALTER TABLE example add ID varchar2 ($);    --3 Updating Data Update  example set id = SID;  --4 Delete the backup data field  ALTER TABLE example drop column SID;  --5 new constraint  ALTER TABLE example ADD constraint exmaple_id primary key (ID);  -----------------------------add constraint--------------------------------------  ALTER TABLE example add Unique (age);  ALTER TABLE example drop unique (age);  --Lookup Table uniqueness constraints (including name, constituent columns)  Select column_name from    user_cons_columns cu, user_constraints au   where Cu.constraint_name = Au.constraint_name and     cu.table_name = ' example ';  

   
   

Oracle field (primary key) type modification method for processing existing data