Here the $1 references the value of the first function argument whenever the function is invoked : Function Parameter « Store Procedure Function « PostgreSQL

1. PostgreSQL
2. Store Procedure Function
3. Function Parameter

Here the $1 references the value of the first function argument whenever the function is invoked

postgres=#
postgres=# CREATE TABLE employee (
postgres(#     ID         int,
postgres(#     name       varchar(10),
postgres(#     salary     real,
postgres(#     start_date date,
postgres(#     city       varchar(10),
postgres(#     region     char(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (1,  'Jason', 40420,  '02/01/94', 'New York', 'W');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (2,  'Robert',14420,  '01/02/95', 'Vancouver','N');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (3,  'Celia', 24020,  '12/03/96', 'Toronto',  'W');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (4,  'Linda', 40620,  '11/04/97', 'New York', 'N');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (5,  'David', 80026,  '10/05/98', 'Vancouver','W');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (6,  'James', 70060,  '09/06/99', 'Toronto',  'N');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (7,  'Alison',90620,  '08/07/00', 'New York', 'W');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (8,  'Chris', 26020,  '07/08/01', 'Vancouver','N');
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (9,  'Mary',  60020,  '06/09/02', 'Toronto',  'W');
INSERT 0 1
postgres=#
postgres=# select * from employee;
 id |  name  | salary | start_date |   city    | region
----+--------+--------+------------+-----------+--------
  1 | Jason  |  40420 | 1994-02-01 | New York  | W
  2 | Robert |  14420 | 1995-01-02 | Vancouver | N
  3 | Celia  |  24020 | 1996-12-03 | Toronto   | W
  4 | Linda  |  40620 | 1997-11-04 | New York  | N
  5 | David  |  80026 | 1998-10-05 | Vancouver | W
  6 | James  |  70060 | 1999-09-06 | Toronto   | N
  7 | Alison |  90620 | 2000-08-07 | New York  | W
  8 | Chris  |  26020 | 2001-07-08 | Vancouver | N
  9 | Mary   |  60020 | 2002-06-09 | Toronto   | W
(9 rows)

postgres=#
postgres=#
postgres=# CREATE FUNCTION myFunction(text) RETURNS employee
postgres-#    AS $$ SELECT * FROM employee WHERE name = $1 $$
postgres-#    LANGUAGE SQL;
CREATE FUNCTION
postgres=#
postgres=# -- Here the $1 references the value of the first function argument whenever the function is invoked.
postgres=#
postgres=#
postgres=# select * from myFunction('James');
 id | name  | salary | start_date |  city   | region
----+-------+--------+------------+---------+--------
  6 | James |  70060 | 1999-09-06 | Toronto | N
(1 row)

postgres=#
postgres=#
postgres=# drop function myFunction(text);
DROP FUNCTION
postgres=# drop table employee;
DROP TABLE
postgres=#
postgres=#
           
       

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