left-join
Two SQL LEFT JOINS produce incorrect result
Joins are processed left to right (unless parentheses dictate otherwise). If you LEFT JOIN (or just JOIN, similar effect) three groceries to one user you get 3 rows (1 x 3). If you then join 4 fishmarkets for the same user, you get 12 (3 x 4) rows, multiplying the previous count in the result, …
Deleting using LEFT JOIN
SAMPLE. DELETE RECORD IN TABLE ‘A’ IS THERE ARE NOT RECORD IN TABLE ‘H’ DELETE A FROM ARTICULO_ALMACEN A LEFT JOIN HISTORICO_UNION H ON A.COD_ARTICULO = H.COD_ARTICULO AND A.COD_ALMACEN = H.COD_ARTICULO_ALMACEN AND A.TPROPIEDAD1 = H.PROPIEDAD1 AND A.TPROPIEDAD2 = H.PROPIEDAD2 AND A.TPROPIEDAD3 = H.PROPIEDAD3 WHERE H.COD_ARTICULO IS NULL
Postgres: left join with order by and limit 1
Use a dependent subquery with max() function in a join condition. Something like in this example: SELECT * FROM companies c LEFT JOIN relationship r ON c.company_id = r.company_id AND r.”begin” = ( SELECT max(“begin”) FROM relationship r1 WHERE c.company_id = r1.company_id ) INNER JOIN addresses a ON a.address_id = r.address_id demo: http://sqlfiddle.com/#!15/f80c6/2
Isn’t SQL A left join B, just A?
No, since it’s a join, it can produce cardinalities greater than 1 for the rows in A. That is, if there are multiple matching rows from B then a row in A will show up multiple times. Example: Table A: id name — ——- 1 Alice 2 Malcolm 3 Kelly Table B: id_a preferred_food —- …
SQL LEFT-JOIN on 2 fields for MySQL
select a.ip, a.os, a.hostname, a.port, a.protocol, b.state from a left join b on a.ip = b.ip and a.port = b.port
LINQ Inner-Join vs Left-Join
I think if you want to use extension methods you need to use the GroupJoin var query = people.GroupJoin(pets, person => person, pet => pet.Owner, (person, petCollection) => new { OwnerName = person.Name, Pet = PetCollection.Select( p => p.Name ) .DefaultIfEmpty() } ).ToList(); You may have to play around with the selection expression. I’m not …
Using left join and inner join in the same query
I always come across this question when searching for how to make LEFT JOIN depend on a further INNER JOIN. Here is an example for what I am searching when I am searching for “using LEFT JOIN and INNER JOIN in the same query”: SELECT * FROM foo f1 LEFT JOIN (bar b1 INNER JOIN …
Symfony2 QueryBuilder join ON and WITH difference
@florian gave you the correct answer but let me try to explain it on example: In sql, joins are done like this: SELECT * FROM category LEFT JOIN product ON product.category_id = category.id (or something like this) Now in Doctrine, you don’t need to use ON clause because doctrine knows that from relations annotations in …
SQL Server Left Join With ‘Or’ Operator
Given how little of the query is being exposed; a very rough rule of thumb is to replace an Or with a Union to avoid table scanning. Select.. LEFT JOIN Child c ON c.ParentAId = a.ParentAId union Select.. left Join Child c ON c.ParentBId = b.ParentBId