How to concat variable to other variable in postgresql? - sql

Question

In php connecting variable using . (dot), like $a = "tes", $b="b", if
I connect $a.$b it becomes "tesb". I want this but in postgres
I have tried using dot and + but wrong
my code
CREATE OR REPLACE FUNCTION make_ctx_contoh (rl varchar, dat varchar)
RETURNS numeric AS $total$
declare
date_before date;
dan text;
os_l numeric;
BEGIN
date_before = (DATE_TRUNC('month', NOW())
+ '0 MONTH'::INTERVAL
- '1 DAY'::INTERVAL)::DATE;
if rl = 'nasional' THEN
dan = '';
ELSEIF rl = 'kanwil' THEN
dan = 'AND LOWER(a."KANWIL") = knw';
ELSEIF rl = 'kc' THEN
dan = 'AND LOWER(a."KC") = kac';
END IF;
SELECT
SUM("a"."OUTSTANDING") into os_l
FROM
"public".tbl_nominatif_hasil AS "a"
WHERE
"a"."BUSS_DATE" = date_before AND
"a"."COLLDET" = '1 ' + dan; RETURN os_l;
END; $total$ LANGUAGE plpgsql;
When I run select make_ctx_contoh('kanwil','2'); that shows error like :
ERROR: operator does not exist: unknown + text LINE 6:
"a"."COLLDET" = '1 ' + dan

Answer 1

From what I could understand from your code, you want to add conditions to the where clause based on certain criteria.
So, convert your select query into a AND OR logic.
SELECT
SUM("a"."OUTSTANDING") into os_l
FROM "public".tbl_nominatif_hasil AS "a"
WHERE "a"."BUSS_DATE" = date_before AND
"a"."COLLDET" = 1
AND ( rl = 'nasional' OR
( rl = 'kanwil' AND LOWER(a."KANWIL") = knw) OR
( rl = 'kc' AND LOWER(a."KC") = kac')
)