How to use the ELSIF statement in Postgres - postgresql

Question

I'm wondering if I can run the if statement by itself, or it can't stand on its own, has to be in a nested statement. I can't directly run the following code.
IF tax_year=2005 THEN
UPDATE table1 SET column1=column1*3;
ELSIF tax_year=2006 THEN
UPDATE table1 SET column1=column1*5;
ELSIF tax_year=2007 THEN
UPDATE table1 SET column1=column1*7;
END IF;
Also, I didn't write it out that when tax_year=2008, column1=column1. I'm not sure if it needs to be in the code since column1 won't change in 2008.
Thanks for your help!

Answer 1

IF / ELSIF / ELSE is part of PL/pgsql, which is an extension of pg, and it's enabled for new database by default.
You can create a function to wrap the IF statements. And call the function to execute these statements.
e.g
-- create function,
CREATE OR REPLACE FUNCTION fun_dummy_tmp(id_start integer, id_end integer) RETURNS setof dummy AS $$
DECLARE
BEGIN
IF id_start <= 0 THEN
id_start = 1;
END IF;
IF id_end < id_start THEN
id_end = id_start;
END IF;
return query execute 'select * from dummy where id between $1 and $2' using id_start,id_end;
return;
END;
$$ LANGUAGE plpgsql;
-- call function,
select * from fun_dummy_tmp(1, 4);
-- drop function,
DROP FUNCTION IF EXISTS fun_dummy_tmp(integer, integer);
And, there is a CASE statement, which might be a better choice for your requirement.
e.g
-- create function,
CREATE OR REPLACE FUNCTION fun_dummy_tmp(id integer) RETURNS varchar AS $$
DECLARE
msg varchar;
BEGIN
CASE id%2
WHEN 0 THEN
msg := 'even';
WHEN 1 THEN
msg := 'odd';
ELSE
msg := 'impossible';
END CASE;
return msg;
END;
$$ LANGUAGE plpgsql;
-- call function,
select * from fun_dummy_tmp(6);
-- drop function,
DROP FUNCTION IF EXISTS fun_dummy_tmp(integer);
You can refer to postgresql document for control statement for the details.

Answer 2

I did it with the following code:
-- UPDATE houston_real_acct_1single1property
-- SET convert_market_value=
-- CASE
-- WHEN tax_year=2005 THEN total_market_value*1.21320615034169
-- WHEN tax_year=2006 THEN total_market_value*1.17961794019934
-- WHEN tax_year=2007 THEN total_market_value*1.15884093604151
-- WHEN tax_year=2008 THEN total_market_value*1.12145267335906
-- WHEN tax_year=2009 THEN total_market_value*1.11834431349904
-- WHEN tax_year=2010 THEN total_market_value*1.0971664297633
-- WHEN tax_year=2011 THEN total_market_value*1.06256515125065
-- WHEN tax_year=2012 THEN total_market_value*1.04321957955664
-- WHEN tax_year=2013 THEN total_market_value*1.02632796014915
-- WHEN tax_year=2014 THEN total_market_value*0.998472101797389
-- WHEN tax_year=2015 THEN total_market_value
-- END;