As the docs you quote indicate, you can’t use $lookup on a sharded collection. So the best practice workaround is to perform the lookup yourself in a separate query. Perform your aggregate query. Pull the “localField” values from your query results into an array, possibly using Array#map. Perform a find query against the “from” collection, … Read more
Move the b condition from WHERE to ON to get a real LEFT JOIN. (With the b condition in the WHERE clause, it executes as a regular inner join…) select a.id, a.name, b.store, b.stock from products a left join stock b on a.id = b.id and b.store=”001″ order by a.id
I am not sure about your requirement. What I understood from your question is you want to delete all the emails of jobs which are closed. try this one; DELETE e FROM emailNotification e LEFT JOIN jobs j ON j.jobId = e.jobId WHERE j.active = 1 AND CURDATE() < j.closeDate
Currently, the theta-style on joining the unrelated classes in the where clause using HQL only supports inner join. The request for supporting the outer join for such situation is currently the 3-rd most voted enhancement but I don’t think this feature will be implemented in the near feature as it requires the re-implementation of the … Read more
After playing around a bit, this turns out to be trickier than I’d expected! Assuming that table_b has some single column that is unique (say, a single-field primary key), it looks like you can do this: SELECT table_a.code, table_a.emp_no, table_b.city, table_b.county FROM table_a LEFT JOIN table_b ON table_b.code = table_a.code AND table_b.field_that_is_unique = ( SELECT … Read more
In Oracle we don’t include the AS when declaring a table alias. Instead of ) AS TABLE_RESOLVERS write ) TABLE_RESOLVERS This is one example when Oracle syntax is more restrictive than some other flavours of SQL. It is also inconsistent with the declaration of column aliases, which is unfortunate but almost certainly it’s too complex … Read more
SELECT p.pid, p.cid, p.pname, c1.name1, c2.name2 FROM product p LEFT JOIN customer1 c1 ON p.cid = c1.cid LEFT JOIN customer2 c2 ON p.cid = c2.cid
left join two tables with a where condition It’s typically wrong to use a LEFT [OUTER] JOIN and then filter with a WHERE condition, thereby voiding the special feature of a LEFT JOIN to include all rows from the left table unconditionally. Detailed explanation: Explain JOIN vs. LEFT JOIN and WHERE condition performance suggestion in … Read more
SELECT a.nid, GROUP_CONCAT(b.name ORDER BY b.id) DepartmentName FROM Notes a INNER JOIN Positions b ON FIND_IN_SET(b.id, a.forDepts) > 0 GROUP BY a.nid SQLFiddle Demo
In data.table, joins of the form x[i] traditionally uses values from i but uses column names from x. Even though this is different from SQL which returns both, this default makes a lot of sense for equi joins since we are interested in all rows from i and if they match then both data.tables have … Read more