Why is it that in PostgreSQL you cannot use:
FULL OUTER JOIN
. . .
ON POSITION(table1.column1 IN table2.column1) <> 0,
But you can accomplish the same thing with a left join and a right join and then using a union all to join the results. It's the same exact result set that I want and I feel it should be possible since it's possible to just do the right and left join manually. I can live with having to do it, but it'd be a lot simpler to write with just using a Full Outer Join.
Related
I prefer to indicate join types when I use it in database systems but when I switch to a new project, there is a single join is used. Generally I prefer to use LEFT JOIN or INNER JOIN according to my needs, but I have not found which JOIN type is considered when a single JOIN is used in PostgreSQL.
select p.uuid from Product s " +
join Category c on p.uuid = c.siteUuid
join Brand b on b.uuid = c.brandUuid
Inner Join is the default join when we use plain JOIN.
For better readablity of the queries, It is always preferred to write INNER JOIN
Reference:
https://www.postgresql.org/docs/current/queries-table-expressions.html#id-1.5.6.6.5.6.4.3.1.2
As the title suggests, does an equal to the lateral join exist in redshift? I haven't run into a situation where it might be necessary yet, but it seems hard to imagine replicating the functionality of a lateral join if I needed to with what I know now.
I needed to perform a right outer join in Mongo db. I know we can use $lookup to perform left outer join. I needed to know is there any way to perform right outer join in Mongo db?
Table A Left Outer Join Table Band Table B Right Outer Join Table A are equivalent in the SQL world only difference you will have is the order of the columns.
Similarly Use $lookup in mongodb which performs a left outer join. Since your requirement is to perform Right Outer Join, reverse the order of the collections.
Take this sample code...
SELECT Persons.name,
getCarModelID(Persons.ID) AS car_model -- < A function
FROM Persons
LEFT OUTER JOIN Cars ON getCarModelID(Persons.ID) = Cars.ID
In the sample above, is it correct to use "LEFT OUTER JOIN"?
If you are planning to join a table with a function then you will need to use the T-SQL "Outer Apply" operator. Similar to Left Join you used and the above will be possible.
Joins can only join two or more tables but not a table with a function.
You can learn using Apply from this link.
The correct code will be as:
SELECT Persons.name,
getCarModelID(Persons.ID) AS car_model -- < A function
FROM Persons
OUTER APPLY Cars ON getCarModelID(Persons.ID) = Cars.ID;
I have a fairly conventional set of order entry tables divided by:
Orders
OrdersRows
OrdersRowsOptions
The record in OrderRowOptions is not created unless needed. When I create a set of joins like
select * from orders o
inner join OrdersRows r on r.idOrder = o.idOrder
inner join ordersrowsoptions ro on ro.idOrderRow = r.idOrderRow
where r.idProduct = [foo]
My full resultset is blank if no ordersrowsoptions records exist for the given product.
what's the correct syntax to return records even if no records exist at one of the join clauses?
thx
select * from orders o
inner join OrdersRows r on r.idOrder = o.idOrder
left join ordersrowsoptions ro on ro.idOrderRow = r.idOrderRow
where r.idProduct = [foo]
Of course you should not use select * in any query but especially never when doing a join. The repeated fields are just wasting server and network resources.
Since you seem unfamiliar with left joins, you probably also need to understand the concepts in this:
http://wiki.lessthandot.com/index.php/WHERE_conditions_on_a_LEFT_JOIN
LEFT JOIN / RIGHT JOIN.
Edit: yes, the following answer, given earlier, is correct:
select * from orders o
inner join OrdersRows r on r.idOrder = o.idOrder
left join ordersrowsoptions ro on ro.idOrderRow = r.idOrderRow
where r.idProduct = [foo]
LEFT JOIN (or RIGHT JOIN) are probably what you are looking for, depending on which side of the join no rows may appear.
Interesting, do you want to get all orders that have that product in them? The other post is correct that you have to use LEFT or RIGHT OUTER JOINS. But if you want to get entire orders that have that product then you'd need a more complex where clause.