I have a table containing a VARRAY of objects as shown below. But I don't know how to find which divisions have...
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an employee called John working in them. How could I look each value of the VARRAY: if the first value is not John, look at the next and so on until I get the value desired, or it realizes that the value doesn't exist?
CREATE OR REPLACE TYPE emp_obj AS OBJECT ( last_name VARCHAR (50), first_name VARCHAR (50), birth_dt DATE ); / CREATE OR REPLACE TYPE emp_va AS VARRAY (999) OF emp_obj; / CREATE TABLE division ( division_id NUMBER (9) PRIMARY KEY, division_name VARCHAR2 (100), emps emp_va );
SELECT e.first_name FROM division d , TABLE (d.emps) e WHERE d.division_name = 'Sales';
You've already done the hard part, isolating one component of each entry in the VARRAY, and you've shown how to use it in a SELECT clause. You can use single elements from the VARRAY in the WHERE clause in exactly the same way:
SELECT DISTINCT d.division_name FROM division d , TABLE (d.emps) e WHERE e.first_name = 'John';what how
SELECT division_name FROM division d WHERE EXISTS ( SELECT 'X' -- Why 'X'? See note below. FROM TABLE (d.emps) WHERE first_name = 'John' );Why 'X'?
This problem does not really revolve around the VARRAY: you could use the same techniques on plain old regular vanilla-flavored relational tables:
-- The straightforward but slower solution SELECT DISTINCT d.division_name FROM division d JOIN emp e USING (division_id) WHERE e.first_name = 'John'; -- The faster but more convoluted solution SELECT division_name FROM division d WHERE EXISTS ( SELECT 'X' FROM emp WHERE first_name = 'John' AND division_id = d.division_id );
If you want run the examples, or to experiment with related questions, you might want to copy these statements to populate the tables.
-- After creating the division table, as shown on the main page, -- the following INSERT statements can be used to populate it. -- The 'Sales' division will have two employees named John. INSERT INTO division ( division_id, division_name, emps ) VALUES ( 1, 'Sales', emp_va ( emp_obj ('Adams', 'John', '30-Oct-1735'), emp_obj ('Adams', 'Abigail', '11-Nov-1744'), emp_obj ('Brown', 'John', ' 9-May-1800') ) ); -- The 'Administration' division will have no employees named John. INSERT INTO division ( division_id, division_name, emps ) VALUES ( 2, 'Administration', emp_va ( emp_obj ('Bingen', 'Hildegard', '17-Sep-1098'), emp_obj ('Bush', 'George W.', ' 6-Jul-1946') ) ); -- Now the SELECT statements (based on the division table, only) -- on the main page will run. CREATE TABLE emp AS SELECT d.division_id , e.last_name , e.first_name , e.birth_dt FROM division d , TABLE (d.emps) e; -- Now the queries on the main page that use the emp table will work.
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