Convert Multiple Row output from SELECT query into Single Row in PostgreSQL

Here is the simple query to convert the result of select query from multiple rows in a table to display as single row,


Simple SELECT query

SELECT str_empno FROM employee;

will return the output like,


Output:

str_empno
-------------
4400100476
4400100563
4400101130
4400101432
4400101501
4400101527
4400101724

by using array_agg and array_to_string function in PostgreSQL,  we can get aggregates/combine/concatenate multiple rows into one row

SELECT array_to_string( array_agg(str_empno),',' ) as  empno FROM employee;

this will return 
Output:

str_empno
-------------

4400100476,4400100563,4400101130,4400101432,4400101501,4400101527,4400101724