I'm not quite sure how to ask for the query I want, so let's start with
data:
create table t1 (i int, val varchar);
insert into t1 values(1,'A B C D');
insert into t1 values(2,'B D E F');
insert into t1 values(3,'G H I J');
create table t2 (q varchar, z varchar);
insert into t2 values('A','vowel');
insert into t2 values('B','consonant');
insert into t2 values('E','vowel');
insert into t2 values('K','consonant');
t1.val will contain "words" separated by blanks. It might be better if
each "word" were a separate row in another table; but that's not how the
legacy database was built. I understand this can be simulated by:
select i,a[s] from (select i, generate_subscripts(string_to_array(val,'
'),1) as s, string_to_array(val,' ') as a from t1) foo;
In my "real life" situation, the "words" are not single letters.
I'd like to write a function that removes selected "words" from t1.val
based on select on t2.
In the above example; let's exclude all vowels, so I end up with:
1 'B C D'
2 'B D F'
3 'G H I J'
For some "words" in val; there may not be a row when joining to t2.q;
these words must be included in final result. In the above example;
there is no row in t2 where q="I"; so it is included in result.
How do I write such a function? Can it be done with SQL only?
