PostgreSQL COUNT Function

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PostgreSQL COUNT function is the simplest function and very useful in counting the number of records, which are expected to be returned by a SELECT statement.

To understand COUNT function consider the table COMPANY having records as follows:

testdb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | James |  24 | Houston   |  10000
(7 rows)

Now suppose based on the above table you want to count total number of rows in this table, then you can do it as follows:

testdb=# SELECT COUNT(*) FROM COMPANY ;

Above PostgreSQL statement will produce the following result:

 count
-------
     7
(1 row)

Similarly, you want to count the number of records for Paul, then it can be done as follows:

testdb=# SELECT COUNT(*) FROM COMPANY WHERE name='Paul';
 count
-------
     1
(1 row)


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