outer query column in inner query case expression - mysql

Question

I am trying to write below query in vertica
`SELECT a.*
FROM a
WHERE a.country="India"
AND a.language ="Hindi"
AND ( CASE WHEN (a.spoken = true
AND exist ( select 1
FROM b
WHERE b.country=a.country
AND b.language=a.language
AND ( CASE WHEN (a.population <b.population
AND a.statsyear > b.statsyear))
THEN true //pick recent stats
WHEN (a.population > b.population)
THEN true
ELSE false
END)) THEN true
WHEN (a.written = true ) THEN
true
ELSE false
END)`
it is not working, because we can't reference "a.population" outer query field in case expression of innerquery. I tried rewriting it wil OR caluse Vertica is not allowing it.
How can I re-write this
I created below tables in MySQL local box
Example of Tables and Results
CREATE TABLE tableA
(
id INT,
country VARCHAR(20),
language VARCHAR(20),
spoken INT,
written INT,
population INT,
stats INT
)
insert into tableA values(1,'India','Hindi',1,0,9,2010)
insert into tableA values(2,'India','Hindi',1,0,11,2011)
insert into tableA values(3,'India','Hindi',1,0,10,2012)
insert into tableA values(4,'India','Hindi',0,1,10,2013)
insert into tableA values(5,'India','Hindi',1,1,10,2012)
insert into tableA values(6,'India','English',1,1,10,2012)
CREATE TABLE tableB
(
id INT,
country VARCHAR(20),
language VARCHAR(20),
population INT,
stats INT
)
insert into TableB values(1,'India','Hindi',10,2009)
insert into TableB values(2,'India','Hindi',10,2011)
insert into TableB values(3,'India','Hindi',10,2012)
Rewrote the query slightly in different way
select distinct a.id
from (
SELECT a.*
FROM TableA a
WHERE a.country="India"
AND a.language ="Hindi" ) a, TableB b
WHere ( CASE WHEN a.written=1 THEN
TRUE
WHEN ( (a.spoken = 1) AND (a.country=b.country) AND (a.language=b.language)) THEN
(case WHEN ((a.population < b.population) AND (a.stats > b.stats)) THEN
TRUE
WHEN (a.population > b.population) THEN
TRUE
ELSE
FALSE
END)
ELSE
FALSE
END)
got below results
1,2,4,5
This is what I need, now could you please help me in writing it more efficient manner

Answer 1

Boolean logic equivalent:
SELECT DISTINCT a.*
FROM TableA a
left join TableB b on a.country=b.country AND a.language=b.language
WHERE a.country='India'
AND a.language ='Hindi'
AND (
a.written=1
OR
(a.spoken = 1 AND a.population < b.population AND a.stats > b.stats)
OR
a.population > b.population
)
;
Result:
+----+---------+----------+--------+---------+------------+-------+
| id | country | language | spoken | written | population | stats |
+----+---------+----------+--------+---------+------------+-------+
| 1 | India | Hindi | 1 | 0 | 9 | 2010 |
| 2 | India | Hindi | 1 | 0 | 11 | 2011 |
| 4 | India | Hindi | 0 | 1 | 10 | 2013 |
| 5 | India | Hindi | 1 | 1 | 10 | 2012 |
+----+---------+----------+--------+---------+------------+-------+
Demo