PostgreSQL 9.5 IF-THEN-ELSE inside FUNCTION not available? - postgresql

Question

My problem
While trying to CREATE a FUNCTION in my PostgreSQL database, version 9.5, I get the following error:
ERROR: syntax error at or near "IF"
LINE 3: IF strpos(trem_outcome, 'VALIDATED') = 0 THEN
Here's the FUNCTION I'm talking about:
CREATE OR REPLACE FUNCTION countValid(outcome text) RETURNS integer AS $$
BEGIN
IF strpos(outcome, 'VALIDATED') = 0 THEN
RETURN 1;
END IF;
RETURN 0;
END
$$ LANGUAGE SQL
Looks like the IF-THEN-ELSE control statements aren't available to me here, although I'm inside a FUNCTION right?
What am I missing?
Some context
I ultimately wanna sum(countValid()) of a huge set of data, like follows:
SELECT
table1.tbl1_pk,
count(table2.tbl2_outcome) as registered,
sum(countValid(table2.tbl2_outcome)) as validated
FROM table1 JOIN table2 ON table2.tbl2_tbl1_fk = table1.tbl1_pk
GROUP BY table1.tbl1_pk;
Where my tables are like:
+---------------------------------------+
| table1 |
+---------------+-----------------------+
| tbl1_pk (int) | tbl1_other_crap (w/e) |
+---------------+-----------------------+
| 1 | ... |
| 2 | ... |
| 3 | ... |
+---------------+-----------------------+
+------------------------------------------------+
| table2 |
+---------+-----------------------+--------------+
| tbl2_pk | tbl2_tbl1_fk | tbl2_outcome |
| (int) | (int -> tbl1.tbl1_pk) | (text) |
+---------+-----------------------+--------------+
| 1 | 1 | VALIDATED |
| 2 | 1 | FLUNKED |
| 3 | 3 | VALIDATED |
| 4 | 3 | VALIDATED |
| 5 | 1 | FLUNKED |
| 6 | 2 | VALIDATED |
| 7 | 3 | VALIDATED |
+---------+-----------------------+--------------+
I'd expect the following result set:
+---------------+------------------+-----------------+
| tbl1_pk (int) | registered (int) | validated (int) |
+---------------+------------------+-----------------+
| 1 | 3 | 1 |
| 2 | 1 | 1 |
| 3 | 3 | 3 |
+---------------+------------------+-----------------+
Minimal reproducible example
I can reproduce my issue on an even simpler function:
CREATE OR REPLACE FUNCTION countValid(outcome text) RETURNS integer AS $$
BEGIN
IF 1 = 1 THEN
RETURN 1;
END IF;
RETURN 0;
END
$$ LANGUAGE SQL
... which triggers:
ERROR: syntax error at or near "IF"
LINE 3: IF 1 = 1 THEN
I'm open to entirely different approaches, although I'd much rather have my work executed in a single query.

Answer 1

You do not need that function. Just use
count(table2.tbl2_outcome = 'VALIDATED' or null)