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If Inner Join can be thought of as Cross Join but filtering out the records satisfying the condition, then Left Outer Join is the above, plus 1 record
by JEDI in Programming Languages

If an Inner Join can be thought of as a cross join and then getting the records that satisfy the condition, then a LEFT OUTER JOIN can be thought of as that, plus ONE record on the left table that doesn't satisfy the condition.

In other words, it is not a cross join that "goes easy" on the left records (even when the condition is not satisfied), because then the left record can appe

can the natural-join be seen as a subset of the equi-join and theta-join?
by Alatar in Databases

I have a question regarding relational algebra and how the theta-join, equi-join, and natural-join can be classified in relation to each other.

In a comment on stackoverflow.com sqlvogel quotes E.F. Codd, the computer scientist who invented the relational model for database management, "[the] Natural[-join] is a subset of Equi[-join] which is a subset of Theta[-join]."*

Inner join on a left join makes the left join behave as a inner join
by l1feh4ck3r in Databases

I have a two lookup tables that I want to inner join on each other, however I only want to left join on my data table.

select * from CLIENT

LEFT JOIN or REGULAR JOIN, and how to compare MySql table to an array? Need performance!
by MikeT in Programming Languages

I have six tables: t1, t2, t3, t4, t5, t6. And I also have one main table: main_table. TOTAL 7 TABLES!

Now, I am using SOLR for the searching of classifieds, and the results from solr are put into an array. The array results are ID:nrs which I use to match agains the same ID:s in MySql.

The first column of ALL tables in MySql is called classified_id.

If the u

CRM LINQ Composite join “The method 'Join' is not supported” error
by JSebok in Programming Languages

Im getting a "The method 'Join' is not supported" error... Funny thing is that i simply converted the 1st LINQ into the 2nd version and it doesnt work...

What i wanted to have was LINQ version #3, but it also doesnt work...

This works

var query_join9 = from s in orgSvcContext.CreateQuery(ServiceAppointment.EntityLogicalName)
join b in orgSvcContext.Cr

mysql: How to INNER JOIN a table but limit join to 1 result with the highest vote or count?
by Mansur in Databases

I have 2 tables. One is items and another is votes for those items.

Items table has: |item_id|name|post_date
Votes table has: |votes_id|item_id|answer|total_yes|total_no

What I want to do is show all items based on post_date and show the answer in the votes table with the HIGHEST total_yes. So I want to show only a SINGLE answer from the votes table with

Create a VIEW where a record in t1 is not present in t2 ? Confirmation on Union/Left Join/Inner Join?
by joshboles in Databases

I am trying to make a view of records in t1 where the source id from t1 is not in t2.

Like... "what records are not present in the other table?"

Do I need to include t2 in the FROM clause? Thanks

SELECT t1.fee_source_id, t1.company_name, t1.document
WHERE t1.fee_source_id NOT IN (
SELECT t1.fee_source_id

Difference between Nested loop join and hash join in SQL Server 2008
by qba73 in Databases

What is the primary difference between a nested loop join and a hash join? I dont have any idea about this and all I know is that they appear on the execution plan of a query. Can anyone shed some light on this?

Oracle outer join not giving expected results (behaving like inner join)
by negonicrac in Databases

This query:

select *
from table_a
, table_b
where table_a.id = table_b.id(+)
and table_b.name = 'BENEFICIARY'

returns me no records. table_b has no records with name='BENEFICIARY'. But the outer join should return all records from table_a regardless . No?
The below query returns records from table_a as expected:


Django ForeignKey with null=True, inner join, and left outer join
by cbridi in Web Design

Let's say I have two Django models Person and Company as follows: -

class Company(models.Model):
name = models.CharField()
class Person(models.Model):
last_name = models.CharField(blank=True)
first_name = models.CharField()
company = models.ForeignKey(Company, null=True, blank=True)

A Person may or may not belong to a


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