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Oracle DELETE method
DELETE method in Oracle PL/SQL, removes all elements from any collection type. This operation immediately frees up the memory allocated to the items to be removed.
Syntax of the DELETE method in Oracle PL/SQL
collect_name.DELETE (n_id);
collect_name.DELETE (m_id, n_id);
where:
|
Consider some examples to understand how to use the DELETE collection method in Oracle PL/SQL.
DELETE method with Nested Tables
In this example, we use Nested Tables and do the following:
- declare the Nested Tables variable
- initialize it with six elements
- delete and then restore the second item.
- delete a number of items, and then restore one of them.
- and at the end we remove all the elements.
Recovered items take up the same memory as the corresponding deleted items. The print_nt_id procedure prints the Nested Tables variable after initialization and after each DELETE operation.
CREATE OR REPLACE TYPE nt_type_id IS TABLE OF NUMBER;CREATE OR REPLACE PROCEDURE print_nt_id (nt nt_type_id) IS i NUMBER;BEGIN i := nt.FIRST; IF i IS NULL THEN DBMS_OUTPUT.PUT_LINE('nt is empty'); ELSE WHILE i IS NOT NULL LOOP DBMS_OUTPUT.PUT('nt.(' || i || ') = '); print(nt_id(i)); i := nt.NEXT(i); END LOOP; END IF; DBMS_OUTPUT.PUT_LINE('---');END print_nt_id;DECLARE nt nt_type_id := nt_type_id(11, 22, 33, 44, 55, 66);BEGIN print_nt_id(nt); nt.DELETE(2); -- Removes the second element print_nt_id(nt); nt(2) := 2222; -- Restores the second element print_nt_id(nt); nt.DELETE(2, 4); -- Removes the range of elements print_nt_id(nt); nt(3) := 3333; -- Restores the third element print_nt_id(nt); nt.DELETE; -- Removes all elements print_nt_id(nt);END;Result:nt_id.(1) = 11nt_id.(2) = 22nt_id.(3) = 33nt_id.(4) = 44nt_id.(5) = 55nt_id.(6) = 66---nt_id.(1) = 11nt_id.(3) = 33nt_id.(4) = 44nt_id.(5) = 55nt_id.(6) = 66---nt_id.(1) = 11nt_id.(2) = 2222nt_id.(3) = 33nt_id.(4) = 44nt_id.(5) = 55nt_id.(6) = 66---nt_id.(1) = 11nt_id.(5) = 55nt_id.(6) = 66---nt_id.(1) = 11nt_id.(3) = 3333nt_id.(5) = 55nt_id.(6) = 66---nt_id is empty---DELETE method with Associative Arrays
The following example fills in the indexed string and removes all the elements, which frees the memory allocated to them. The example then replaces the deleted items, that is, adds new items that have the same indexes as the deleted items.
The new replacement items do not take up the same memory as the corresponding deleted items. Finally, the example removes one item and then a number of items. The print_aa_str_id procedure shows the effects of operations.
DECLARE
TYPE aa_type_str_id IS TABLE OF INTEGER INDEX BY VARCHAR2(10);
aa_str_id aa_type_str_id;
PROCEDURE print_aa_str_id IS
i VARCHAR2(10);
BEGIN .
i := aa_str_id.FIRST;
IF i IS NULL THEN
DBMS_OUTPUT.PUT_LINE('aa_str_id is empty');
ELSE .
WHILE i IS NOT NULL LOOP
DBMS_OUTPUT.PUT('aa_str_id(' || i || ') = '); print(aa_str_id(i));
i := aa_str_id.NEXT(i);
END LOOP;
END IF;
DBMS_OUTPUT.PUT_LINE('---');
END print_aa_str_id;
BEGIN .
aa_str_id('M') := 13;
aa_str_id('Z') := 26;
aa_str_id('C') := 3;
print_aa_str_id;
aa_str_id.DELETE; -- Delete all elements
print_aa_str_id;
aa_str_id('M') := 13; -- Replaces the removed item with the same value
aa_str_id('Z') := 260; -- Replaces the deleted item with a new value
aa_str_id('C') := 30; -- Replaces the removed item with a new value
aa_str_id('W') := 23; -- Adds a new element
aa_str_id('J') := 10; -- Adds a new element
aa_str_id('N') := 14; -- Adds a new element
aa_str_id('P') := 16; -- Adds a new element
aa_str_id('W') := 23; -- Adds a new element
aa_str_id('J') := 10; -- Adds a new element
print_aa_str_id;
aa_str_id.DELETE('C'); -- Removes one element
print_aa_str_id;
aa_str_id.DELETE('N', 'W'); -- Removes the range of elements
print_aa_str_id;
aa_str_id.DELETE('Z', 'M'); -- Does nothing.
print_aa_str_id;
END;
Result:
aa_str_id.(C) = 3
aa_str_id.(M) = 13
aa_str._id(Z) = 26
---
aa_str_id is empty
---
aa_str._id(C) = 30
aa_str._id(J) = 10
aa_str._id(M) = 13
aa_str._id(N) = 14
aa_str._id(P) = 16
aa_str._id(W) = 23
aa_str._id(Z) = 260
---
aa_str._id(J) = 10
aa_str._id(M) = 13
aa_str._id(N) = 14
aa_str._id(P) = 16
aa_str._id(W) = 23
aa_str._id(Z) = 260
---
aa_str._id(J) = 10
aa_str._id(M) = 13
aa_str._id(Z) = 260
---
aa_str._id(J) = 10
aa_str._id(M) = 13
aa_str._id(Z) = 260
---
Method Delete in Oracle Database
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