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ALTER TABLE AA DROP COLUMN  DEP;
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2¡¢ALTER TABLE AA SET UNUSED("DEP") CASCADE CONSTRAINTS;
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ALTER TABLE AA DROP UNUSED COLUMNS;
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alter table table_name add mmm  varchar2(10);
update table_name set mmm=** ;
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insert into t_address (addressname) (select vcname from busstop)
create sequence seq_id_test_increment    --ÐòÁÐ
increment by 1 start with 1 maxvalue 9999999;   
  
create or replace trigger insert_test_increment    --´¥·¢Æ÷
before insert on t_address    --t_address    ±í
referencing   
new as new   
old as old   
for each row   
begin  
    select seq_id_test_increment.nextval into :new.addressid from dual;    --addressid×Ö¶Î
end;


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int sqlite3_exec(sqlite3*£¬ const char *sql£¬ sqlite3_callbacksql Óï·¨
£¬ void *£¬  char **errmsg );
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NULLIF (expr1, expr2) ->ÏàµÈ·µ»ØNULL£¬²»µÈ·µ»Øex ......

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create or replace trigger del_dept_id
after delete on dept
for each row
begin
delete from emp where deptno=:old.deptno;
end;
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