NEXT Method in PL/SQL โ Navigate to the Next Collection Index
The NEXT Method in PL/SQL is a powerful collection API function that lets you retrieve the next higher subscript value from a given index. Itโs particularly useful when working with sparse collections or associative arrays.
By using the NEXT Method in PL/SQL, you can safely iterate through collections without assuming sequential subscriptsโmaking your code more robust and error-resistant.
What is the NEXT Method in PL/SQL?
The NEXT
method returns the next index value (or subscript) in a collection after a specified one.
Works with numeric and string-based indexes
Returns
NULL
if there is no higher indexRaises an exception if the collection is null (unless checked with
EXISTS
)
Syntax of NEXT Method in PL/SQL
collection_name.NEXT(index_value)
Returns:
PLS_INTEGER
for numeric indexesVARCHAR2
for associative arrays with string indexesNULL
if the passed index is the highest one
Example: Using NEXT Method with String Indexes
DECLARE
TYPE assoc_array IS TABLE OF INTEGER INDEX BY VARCHAR2(10);
my_list assoc_array;
BEGIN
my_list('Apple') := 10;
my_list('Mango') := 20;
my_list('Banana') := 30;
DBMS_OUTPUT.PUT_LINE('FIRST: ' || my_list.FIRST);
DBMS_OUTPUT.PUT_LINE('NEXT of FIRST: ' || my_list.NEXT(my_list.FIRST));
DBMS_OUTPUT.PUT_LINE('LAST: ' || my_list.LAST);
DBMS_OUTPUT.PUT_LINE('NEXT of LAST: ' || TO_CHAR(my_list.NEXT(my_list.LAST)));
END;
/
Output:
FIRST: Apple
NEXT of FIRST: Banana
LAST: Mango
NEXT of LAST:
Explanation
In associative arrays with string keys, PL/SQL internally sorts keys alphabetically based on the current NLS_SORT
session setting. Hereโs the order in the example:
Apple โ Banana โ Mango
Thus:
NEXT('Apple')
returns'Banana'
NEXT('Mango')
returnsNULL
(no higher subscript)
Use Cases of the NEXT Method in PL/SQL
Use Case | Description |
---|---|
Sparse Arrays | Skip over deleted or missing elements |
Associative Arrays | Safely loop through keys |
Dynamic Indexing | Avoid hardcoded index assumptions |
Backward Navigation | Use with PRIOR to go back if needed |
Best Practices for NEXT Method in PL/SQL
Always verify that the collection is not null before using
NEXT
.Combine
FIRST
,NEXT
, andEXISTS
for safe iteration in sparse or associative collections.Do not assume keys are ordered numerically when using string indexes.
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