How do you use variables in a simple PostgreSQL sc

Question

For example, in MS-SQL, you can open up a query window and run the following:

DECLARE @List AS VARCHAR(8)

SELECT @List = 'foobar'

SELECT *
FROM   dbo.PubLists
WHERE  Name = @List

How is this done in PostgreSQL? Can it be done?

Answer 1

For the official CLI client "psql" see here. And "pgAdmin3" 1.10 (still in beta) has "pgScript".

Answer 2

For use variables in for example alter table:

DO $$ 
DECLARE name_pk VARCHAR(200);
BEGIN
select constraint_name
from information_schema.table_constraints
where table_schema = 'schema_name'
      and table_name = 'table_name'
      and constraint_type = 'PRIMARY KEY' INTO name_pk;
IF (name_pk := '') THEN
EXECUTE 'ALTER TABLE schema_name.table_name DROP CONSTRAINT ' || name_pk;

Answer 3

Here's an example of using a variable in plpgsql:

create table test (id int);
insert into test values (1);
insert into test values (2);
insert into test values (3);

create function test_fn() returns int as $$
    declare val int := 2;
    begin
        return (SELECT id FROM test WHERE id = val);
    end;
$$ LANGUAGE plpgsql;

SELECT * FROM test_fn();
 test_fn 
---------
       2

Have a look at the plpgsql docs for more information.

Answer 4

DO $$
DECLARE  
   a integer := 10;  
   b integer := 20;  
   c integer;  
BEGIN  
   c := a + b;
    RAISE NOTICE'Value of c: %', c;
END $$;