What is the difference between JOIN and INNER JOIN?
They are functionally equivalent, but INNER JOIN can be a bit clearer to read, especially if the query has other join types (i.e. LEFT or RIGHT or CROSS) included in it.
They are functionally equivalent, but INNER JOIN can be a bit clearer to read, especially if the query has other join types (i.e. LEFT or RIGHT or CROSS) included in it.
I’m not an SQL tuning expert, but joining hundreds of millions of rows on a VARCHAR field doesn’t sound like a good idea in any database system I know. You could try adding an integer column to each table and computing a hash on the NAME field that should get the possible matches to a … Read more
UPDATE T1 SET T1.Inci = T2.Inci FROM T1 INNER JOIN T2 ON T1.Brands = T2.Brands AND T1.Category= T2.Category AND T1.Date = T2.Date
SELECT `locations`.`name` FROM `locations` INNER JOIN `school_locations` ON `locations`.`id` = `school_locations`.`location_id` INNER JOIN `schools` ON `school_locations`.`school_id` = `schools_id` WHERE `type` = ‘coun’; the WHERE clause has to be at the end of the statement
SELECT * FROM employees e1, employees e2 WHERE e1.phoneNumber = e2.phoneNumber AND e1.id != e2.id; Update : for better performance and faster query its good to add e1 before * SELECT e1.* FROM employees e1, employees e2 WHERE e1.phoneNumber = e2.phoneNumber AND e1.id != e2.id;
There is no reason to ever use an implicit join (the one with the commas). Yes for inner joins it will return the same results. However, it is subject to inadvertent cross joins especially in complex queries and it is harder for maintenance because the left/right outer join syntax (deprecated in SQL Server, where it … Read more
You are probably looking for select_related, which is the natural way to achieve this: pubs = publication.objects.select_related(‘country’, ‘country_state’, ‘city’) You can check the resulting SQL via str(pubs.query), which should result in output along the following lines (the example is from a postgres backend): SELECT “publication”.”id”, “publication”.”title”, …, “country”.”country_name”, … FROM “publication” INNER JOIN “country” ON … Read more
I think I figured it out. In knex.js, say you specify a table like: knex.select( ‘*’ ).from( ‘Users’ ) Then you can just add the AS keyword within the quotes of the table name to alias it, like so: knex.select( ‘*’ ).from( ‘Users AS u’ ) ..and you can do this for column names, too; … Read more
In all modern databases all these constructs are optimized to the same plan. Some databases (like SQL Server) require an ON condition after the INNER JOIN, so your third query just won’t parse there. Visibility scope of the tables is in the JOIN order, so this query: SELECT * FROM s1 JOIN s2 ON s1.id … Read more
Inner joins are probably the best method, and you only need 3. This will give you a result set with two columns: company and associated values. SELECT Table4.company, table1.id, table1.value FROM Table1 INNER JOIN Table2 ON Table2.table1_id = Table1.id INNER JOIN Table3 ON Table3.table2_id = Table2.id INNER JOIN Table4 ON Table4.table3_id = Table3.id