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Size: a a a
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A
SG
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drop table objects;
drop table tasks;
create table objects (
object_id number (38) PRIMARY KEY,
object_descr VARCHAR2(4000)
);
create table tasks (
task_id number(38) PRIMARY KEY ,
object_id NUMBER(38) REFERENCES objects(object_id),
status number(1) CONSTRAINT check_status CHECK (status IN (0,1))
);
CREATE UNIQUE INDEX only_one_active_task ON tasks(object_id,CASE WHEN status = 1 then 1 else NULL END);
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