outer-join

When I do a left outer join, I expect to get all the records that the query would return prior to adding the joined table, but it is only returning records that match the joined table (i.e: no record for '092387' exists in table 'documentation', so I just want null returned for 'filename' field for that record.) What am I doing wrong? mysql> select documentation_reference.ref_docnumber , documentation.filename from documentation_reference left outer join documentation on ref_docnumber=documentation.docnumber where documentation_reference.docnumber='TP-036' and documentation.status!=3; +-------

In the data.table FAQ , the nomatch = NA parameter is said to be akin to an outer join. However, I haven't been able to get data.table to do a full outer join – only right outer joins. For example: a <- data.table("dog" = c(8:12), "cat" = c(15:19)) dog cat 1: 8 15 2: 9 16 3: 10 17 4: 11 18 5: 12 19 b <- data.table("dog" = 1:10, "bullfrog" = 11:20) dog bullfrog 1: 1 11 2: 2 12 3: 3 13 4: 4 14 5: 5 15 6: 6 16 7: 7 17 8: 8 18 9: 9 19 10: 10 20 setkey(a, dog) setkey(b, dog) a[b, nomatch = NA] dog cat bullfrog 1: 1 NA 11 2: 2 NA 12 3: 3 NA 13 4: 4 NA 14 5: 5 NA 15 6: 6 NA 16 7: 7 NA 17 8: 8 15 18 9

Given: (def seq1 ({:id 1 :val 10} {:id 2 :val 20})) (def seq2 ({:id 1 :val 12} {:id 3 :val 30})) Within each sequence, the :id value is guaranteed to be unique in that sequence, though not necessarily ordered. How can these two sequences of maps be joined by the :id key, so that the result is as shown? {1 [{:id 1 :val 10} {:id 1 :val 12}], 2 [{:id 2 :val 20} nil ], 3 [nil {:id 3 :val 30}]} The ultimate result is a map of pairs. This is similar to a full outer join, where not only the intersection, but also the difference of the two sets is included in the output. Here's the answer I came up

I have a query like this: select a1.name, b1.info from (select name, id, status from table1 a) as a1 right outer join (select id, info from table2 b) as b1 on (a1.id = b1.id) I only want to include everything where a1.status=1 and since I'm using an outer join, I can't just add a where constraint to table1, because all info from table2 that I want to be excluded will still be there, just without the name. I was thinking something like this: select z1.name, z1.info from ((select name, id, status from table1 a) as a1 right outer join (select id, info from table2 b) as b1 on (a1.id = b1.id)) as

Suppose I have two very large lists {a1, a2, …} and {b1, b2, …} where all ai and bj are large sparse arrays. For the sake of memory efficiency I store each list as one comprehensive sparse array. Now I would like to compute some function f on all possible pairs of ai and bj where each result f[ai, bj] is a sparse array again. All these sparse arrays have the same dimensions, by the way. While Flatten[Outer[f, {a1, a2, ...}, {b1, b2, ...}, 1], 1] returns the desired result (in principle) it appears to consume excessive amounts of memory. Not the least because the return value is a list of