Suppose that you have a comma delimited line of department numbers and you need to get a comma delimited line of department names. Apparently, you could write a PL/SQL block, loop through the list of departments and concatenate them in a single text string. However, with a new powerful built-in function listagg that was introduced in Oracle 11gR2 you can accomplish the task in a single SELECT statement.
The idea is to split the ids first using approach I presented in a previous post and then use LISTAGG function to assemble the result character string.
var department_numbers VARCHAR2(200) exec :department_numbers:='10,20,40' col dept_names for a80 WITH x AS ( SELECT REGEXP_SUBSTR(:department_numbers, '[^,]+', 1, LEVEL) deptno FROM dual CONNECT BY LEVEL <= LENGTH(:department_numbers)-LENGTH(REPLACE(:department_numbers,','))+1 ) SELECT listagg (dname, ', ') WITHIN GROUP (ORDER BY dname) AS dept_names FROM dept d JOIN x ON d.deptno=x.deptno;
DEPT_NAMES ---------------------------------- ACCOUNTING, OPERATIONS, RESEARCH
For more tricks and cool techniques check my book “Oracle SQL Tricks and Workarounds” for instructions.