Oracle | Collection Functions

Oracle Collection Functions Version 21c

General Information

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Collection functions operate on nested tables and varrays

CARDINALITY

Returns the number of elements in a nested table CARDINALITY(collection IN "<TABLE_1>") RETURN PLS_INTEGER;

See Nested Table and Collections Demos

COLLECT

Takes a column of any type and creates a nested table of the input type out of the rows selected COLLECT(<column>)

conn sh/sh@pdbdev

      

      CREATE OR REPLACE TYPE phone_book_t AS TABLE OF VARCHAR2(25);

      /

      

      SELECT CAST(COLLECT(cust_main_phone_number) AS phone_book_t)

      FROM customers

      WHERE cust_id BETWEEN 1 AND 5;

      

      SELECT CAST(COLLECT(cust_credit_limit) AS phone_book_t)

      FROM customers

      WHERE cust_id BETWEEN 1 AND 5;

      

      WITH q AS (SELECT CAST(COLLECT(cust_credit_limit) AS phone_book_t)

      FROM customers

      WHERE cust_id BETWEEN 1 AND 5)

      SELECT COUNT(*) FROM TABLE(q);

POWERMULTISET

Takes a nested table and returns a nested table of nested tables containing all nonempty subsets (called submultisets) of the input nested table

Note: This demo, and the following two, are copied from the tahiti docs but put onto a single page to make using them easier POWERMULTISET(<expression>)

conn oe/oe@pdbdev

      

      CREATE TABLE customers_demo AS

      SELECT * FROM customers;

      

      CREATE OR REPLACE TYPE cust_address_tab_typ AS

      TABLE OF cust_address_typ;

      /

      

      ALTER TABLE customers_demo

      ADD (cust_address_ntab cust_address_tab_typ, cust_address2_ntab cust_address_tab_typ)

      NESTED TABLE cust_address_ntab STORE AS cust_address_ntab_store

      NESTED TABLE cust_address2_ntab STORE AS cust_address2_ntab_store;

      

      UPDATE CUSTOMERS_DEMO cd

      SET cust_address_ntab = 

      CAST(MULTISET(SELECT cust_address

      FROM customers c

      WHERE c.customer_id =

      cd.customer_id) as cust_address_tab_typ);

      

      UPDATE CUSTOMERS_DEMO cd

      SET cust_address2_ntab = 

      CAST(MULTISET(SELECT cust_address

      FROM customers c

      WHERE c.customer_id =

      cd.customer_id) as cust_address_tab_typ);

      

      COMMIT;

      

      SELECT parent_table_name, table_name, table_type_name

      FROM user_nested_tables;

      

      CREATE OR REPLACE TYPE cust_address_tab_tab_typ

      AS TABLE OF cust_address_tab_typ;

      /

      

      SELECT CAST(POWERMULTISET(cust_address_ntab) AS cust_address_tab_tab_typ)

      FROM customers_demo;

POWERMULTISET_BY_CARDINALITY

Takes a nested table and a cardinality and returns a nested table of nested tables containing all non-empty subsets (called submultisets) of the nested table of the specified cardinality POWERMULTISET_BY_CARDINALITY(<expression>, <cardinality>)

UPDATE customers_demo

      SET cust_address_ntab = cust_address_ntab MULTISET UNION cust_address_ntab;

      

      SELECT CAST(POWERMULTISET_BY_CARDINALITY(cust_address_ntab, 2)

      AS cust_address_tab_tab_typ)

      FROM customers_demo;

SET

Converts a nested table into a set by eliminating duplicates SET(<nested_table>)

SELECT customer_id, SET(cust_address_ntab) address

      FROM customers_demo;