" Sort Key: coauth.source, coauth.target, coauth.year" " -> Index Only Scan using combinations_source_target_year_idx on combinations comb (cost=371.45 rows=146636992 width=18)" " Merge Cond: ((comb.source = coauth.source) AND (comb.target = coauth.target) AND (comb.year = coauth.year))" " Merge Cond: ((comb.source = adj.source) AND (comb.target = adj.target) AND (comb.year = adj.year))" Should I merge the keys so that I don't merge on multiple columns but just one? Should I join some tables separately so that in the end I only merge two tables? Should I not use postgres at all? I'm grateful for any help in this regard. Given that the tables are not indexed, which method should I use? From pgadmin's help page it looks like both hash and GiST seem appropriate. How can I improve the merge design? I have some freedom over the table look like. Then I proceeded to export the view like so: psql -U postgres -d department-networks -c "COPY master TO stdout DELIMITER ',' CSV HEADER " > ~/master.csv LEFT JOIN adjacencies adj ON comb.source = adj.source AND comb.target = adj.target AND comb.year = adj.year LEFT JOIN coauthorships coauth ON comb.source = coauth.source AND comb.target = coauth.target AND comb.year = coauth.year This is the definition of view master: SELECT comb.source, My initial idea was to construct a view and export the view to disk. All tables have non-clustered indices on (source, target, year) Each row in each table is uniquely identified by (source,target,year). Source | target | year | auth_first_order | auth_second_order | com_first_order | com_second_orderīigint | bigint | smallint | double | double | double | doubleĮventually there will be more tables. I have the following tables: combinations (121M rows) I am wondering what slows my join operation down the most: Having many rows, merging on multiple columns, or mergng multiple tables. My only aim with this database is to merge multiple datasets (tables) and extract the final table. I would like a way to JOIN all of these tables together.I am using PostgreSQL via pgadmin3 on Ubuntu 16.04 with 7.7GiB Memory and 4x.3GHz processor. I'm guessing it is because that is not how you are supposed to name/reference JOINS. However, this gives me the error invalid reference to FROM-clause entry for table "t1". ON t5.section_identifer = t6.section_identifer INNER JOIN (course1 t3 INNER JOIN section1 t4 ON t3.course_number = t4.course_number) t6 I put together a nested statement that I thought would work: SELECT t1.name, t3.departmentįROM (student1 t1 INNER JOIN grade_report1 t2 ON t1.student_number = t2.student_number) t5 Section_identifer INTEGER NOT NULL PRIMARY KEY,įOREIGN KEY (course_number) REFERENCES course1(course_number) ON DELETE CASCADEįOREIGN KEY (student_number) REFERENCES student1(student_number) ON DELETE CASCADE,įOREIGN KEY (section_identifer) REFERENCES section1(section_identifer) ON DELETE CASCADE Student_number INTEGER NOT NULL PRIMARY KEY, I want to return all the student names and department names of all students that achieved grade A. I'm practising for an upcoming database exam and I'm trying to get my head around nested and multiple joins in SQL, specifically the Postgresql syntax.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |