I have a requirement something like there are two db tables A and B.
Table A and table B both have column 'merit' of type integer. The requirement is to find the entries from table A those have merit that matches with the least merit number in table B.
If merit in B is NULL for all the entries, the query should result all the entries from table A.
If merit in B has valid numbers, the query should result the entries of A those match the least merit number in table B.
Sample data is like this::
TABLE A TABLE B
COL1 COL2 MERIT COL1 COL2 MERIT
a ab 1 c ac 1
b bc 2 d ad 3
From above data the least merit in B is 1 so, only the matching entry should result from Table A.
If merit column in B is null for all the entries ie. B has no valid number for merit, two entries from A should result.
So, I came up with the below sql query::
select A.* from A where A.merit IS NOT DISTINCT FROM (
select min(B.merit) from B where B.merit IS NOT NULL);
I am unable to write the JPA equivalent of this sql because of "IS NOT DISTINCT FROM".
The below queries are not working.
select a from A a where a.merit in (select min(b.merit) from B b where b.merit is not null)
select a from A a where a.merit = (select min(b.merit) from B b where b.merit is not null)
My environment is POSTGRESQL, HIBERNATE in QUARKUS.
Thanks for any suggestions.
Related
In a Postgres DB, I have 2 varchar[] columns in 2 tables with common ID that contain data as below:
I need to return rows where all values of t_col are present in f_col (with or without extra data).
Desired result:
I tried with the below as conditions in self join query.
select
from t1 a, t2 b
where a.id=b.id
not (a.f_col #> b.t_col)
Table a has 100 row with name columns.
Table b is the same structure as Table A, but has 10 million rows.
Create a query to verify that the value of table a is not in table b.
However, comparing the value of table a with the value of table b takes too long.
I want to complete the work in 5 seconds, but I don't know how.
Below is the method I tried. Both table name columns have b-tree indexes.
1.
select
name
from
a
where
and not exists (select
name
from
b
where
a.name = b.name
);
select
a.name
from
a left outer join b
on a.name = b.name
where
b.name is null;
You want the following index on the B table:
CREATE INDEX name_idx ON b (name);
This should allow Postgres to rapidly lookup any of the 100 names in the a table against the above index. This should avoid the need to do a full table scan of the b table, which, as you are seeing, can be costly.
Advanced case when statement in T-SQL using three columns
Hope someone can help with the following :)
I have two tables in SQL.
Table 1 has 4 columns - person_id, A, B, and C.
Table 2 has 3 look-up columns - A, B, and C
I want to carry out the following:
Look down Table 1, column A, find value in Table 2, column A
If no value, go to Table 1, column B.
Look down Table 1, column B, find value in Table 2, column B
If no value, go to Table 1, column C
Look down Table 1, column C, find value in Table 2, column C
If no values in any column put 'Null'
So I know how to write a simple case when statement. However, I think that 'case when' only works on one column. I've started to write out the code but need help to get it right.
Select person_id,
case when 1.A is not null then 2.A
when 1.B is not null then 2.B
else 1.C
end as CODE
from table 1
left join table 2
Order by person_id
Would appreciate any help you can give, thank you.
Your sql seems mostly correct, except for the else 1.C.
Since a CASE WHEN will return 1 value, depending on the first positive WHEN criteria.
And a CASE returns NULL as default.
So ELSE null isn't really needed.
The table descriptions do indicate that Table2 only contains 1 row.
If so, then you can cross join them.
SELECT t1.person_id,
CASE
WHEN t1.A IS NOT NULL THEN t2.A
WHEN t1.B IS NOT NULL THEN t2.B
WHEN t1.C IS NOT NULL THEN t2.C
END AS [CODE]
FROM [Table 1] t1
CROSS JOIN (
SELECT TOP 1 A, B, C
FROM [Table 2]
ORDER BY A DESC, B DESC, C DESC
) t2
I have two tables A and B.
Both the tables have same number of columns.
Table A always contains all ids of Table B.
Need to fetch row from Table B first if it does not exist then have
to fetch from Table A.
I was trying to dynamically do this
select
CASE
WHEN b.id is null THEN
a.*
ELSE
b.*
END
from A a
left join B b on b.id = a.id
I think this syntax is not correct.
Can some one suggest how to proceed.
It looks like you want to select all columns from table A except when a matching ID exists in table B. In that case you want to select all columns from table B.
That can be done with this query as long as the number and types of columns in both tables are compatible:
select * from a where not exists (select 1 from b where b.id = a.id)
union all
select * from b
If the number, types, or order of columns differs you will need to explicitly specify the columns to return in each sub query.
In PostgreSQL, I have N tables, each consisting of two columns: id and value. Within each table, id is a unique identifier and value is numeric.
I would like to join all the tables using id and, for each id, create a sum of values of all the tables where the id is present (meaning the id may be present only in subset of tables).
I was trying the following query:
SELECT COALESCE(a.id, b.id, c.id) AS id,
COALESCE(a.value,0) + COALESCE(b.value,0) + COALESCE(c.value.0) AS value
FROM
a
FULL OUTER JOIN
b
ON (a.id=b.id)
FULL OUTER JOIN
c
ON (b.id=c.id)
But it doesn't work for cases when the id is present in a and c, but not in b.
I suppose I would have to do some bracketing like:
SELECT COALESCE(x.id, c.id) AS id, x.value+c.value AS value
FROM
(SELECT COALESCE(a.id, b.id), a.value+b.value AS value
FROM
a
FULL OUTER JOIN
b
ON (a.id=b.id)
) AS x
FULL OUTER JOIN
c
ON (x.id = c.id)
It was only 3 tables and the code is ugly enough already imho. Is there some elegant, systematic ways how to do the join for N tables? Not to get lost in my code?
I would also like to point out that I did some simplifications in my example. Tables a, b, c, ..., are actually results of quite complex queries over several materialized views. But the syntactical problem remains the same.
I understood you need to sum the values from N tables and group them by id, correct?
For that I would do this:
Select x.id, sum (x.value) from (
Select * from a
Union all
Select * from b
Union all........
) as x group by x.id;
Since the n tables are composed by the same fields you can union them all creating a big table full of all the id - value tuples from all tables. Use union all because union filters for duplicates!
Then just sum all the values grouped by id.