BULK COLLECT
Ø This is used for array fetches
Ø With this you can retrieve multiple rows of data with a single roundtrip.
Ø This reduces the number of context switches between the pl/sql and sql engines.
Ø Reduces the overhead of retrieving data.
Ø You can use bulk collect in both dynamic and static sql.
Ø You can use bulk collect in select, fetch into and returning into clauses.
Ø SQL engine automatically initializes and extends the collections you reference in the bulk collect clause.
Ø Bulk collect operation empties the collection referenced in the into clause before executing the query.
Ø You can use the limit clause of bulk collect to restrict the no of rows retrieved.
Ø You can fetch into multible collections with one column each.
Ø Using the returning clause we can return data to the another collection.
BULK COLLECT IN FETCH
Ex:
DECLARE
Type t is table of dept%rowtype;
nt t;
Cursor c is select *from dept;
BEGIN
Open c;
Fetch c bulk collect into nt;
Close c;
For i in nt.first..nt.last loop
dbms_output.put_line('Dname = ' || nt(i).dname || ' Loc = ' || nt(i).loc);
end loop;
END;
Output:
Dname = ACCOUNTING Loc = NEW YORK
Dname = RESEARCH Loc = DALLAS
Dname = SALES Loc = CHICAGO
Dname = OPERATIONS Loc = BOSTON
BULK COLLECT IN SELECT
Ex:
DECLARE
Type t is table of dept%rowtype;
Nt t;
BEGIN
Select * bulk collect into nt from dept;
for i in nt.first..nt.last loop
dbms_output.put_line('Dname = ' || nt(i).dname || ' Loc = ' || nt(i).loc);
end loop;
END;
Output:
Dname = ACCOUNTING Loc = NEW YORK
Dname = RESEARCH Loc = DALLAS
Dname = SALES Loc = CHICAGO
Dname = OPERATIONS Loc = BOSTON
LIMIT IN BULK COLLECT
Ex:
DECLARE
Type t is table of dept%rowtype;
nt t;
Cursor c is select *from dept;
BEGIN
Open c;
Fetch c bulk collect into nt;
Close c;
For i in nt.first..nt.last loop
dbms_output.put_line('Dname = ' || nt(i).dname || ' Loc = ' || nt(i).loc);
end loop;
END;
Output:
Dname = ACCOUNTING Loc = NEW YORK
Dname = RESEARCH Loc = DALLAS
