Cross Join + Full Outer Join ?
I desesperately need to cross join 2 rows in a table, like this table :
table values :
env type value
---------------------
env1 a 1
env1 b 2
env2 b 3
env2 c 4
env3 c 5
-> to get another table crossed by env and type like this :
table results :
a b c
----------------------
env1 1 2 null
env2 null 3 4
env3 null null 5
i tried requests using cross join and full outer join but no way, FULL OUTER JOIN is unknow by mysql, indeed i doubt this is the good solution...
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JOIN Within LEFT JOIN
I am using MySQL 3.23.54. I have the following table structure. FORMS form_id (PK) form_name STAFF ASSIGNMENTS staff_assignment_id (PK) form_id (FK) staff_id (FK) STAFF staff_id (PK) first_name last_name For each record in FORMS there may be zero, one or multiple records in STAFF ASSIGNMENTS. I need to perform a left join from FORMS on STAFF_ASSIGNMENTS. When there is a record in STAFF ASSIGNMENTS, I need to perform a join with STAFF to retreive staff name. Here is my attempt at the query. SELECT forms.form_id, forms.form_name, staff.first_name, staff.last_name FROM forms LEFT JOIN staff_assignments ON forms.form_id = staff_assignments.form_id (JOIN staff on staff_assignements.staff_id = staff.staff_id) How do I need to write the query?
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Inner Join Or Left Join?
What I am trying to do is this.... English Table: Number Text Roman 1 One I 2 Two II 3 Three III 4 Four IV Hindi Table: Number Text 2 Do 3 Teen 4 Char 5 Panch Expected Results where number is 2 Text Roman Two II Do II
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Self Join Plus Left Join?
select distinct t2.personid, count(*) from messagexperson as t1, messagexperson as t2 where t1.messageid = t2.messageid and t1.personid = 2877 and t2.personid <> 2877 group by t2.personid like to get the actual names of the other people rather than the person id. Is there a way to combine another join with the self join to accomplish this? I tried inserting a left join in place of the t2 definitions, i.e. select distinct t2.name, count(*) from messagexperson as t1, (messagexperson left join person on messagexperson.personid = person.id) as t2 where t1.messageid = t2.messageid and t1.personid = 2877 and t2.personid <> 2877 group by t2.personid
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To JOIN Or Not To JOIN... Or Am I Missing Something...?
Right, I was always under the impression that it was 'better' to use JOINs, partly because it is 'faster'. I'm now wondering if that is simply a myth. Take these two SQL statements: SELECT DISTINCT p.ProductID, p.Image, p.Price FROMproducts AS p RIGHT JOINcategory_links AS c_l ONc_l.ProductID= p.ProductID INNER JOINcategories AS c ONc.CategoryID= c_l.CategoryID RIGHT JOINbrands AS b ONp.BrandID= b.BrandID RIGHT JOINsize_links AS s_l ONs_l.ProductID= p.ProductID INNER JOINsizes AS s ONs.SizeID= s_l.SizeID RIGHT JOINcolour_links AS co_l ONco_l.ProductID= p.ProductID INNER JOINcolours AS co ONco.ColourID= co_l.ColourID SELECT DISTINCT p.ProductID, p.Image, p.Price FROMproducts AS p, category_links AS c_l, categories AS c, brands AS b, size_links AS s_l, sizes AS s, colour_links AS co_l, colours AS co WHEREc_l.ProductID= p.ProductID ANDc.CategoryID= c_l.CategoryID ANDp.BrandID= b.BrandID ANDs_l.ProductID= p.ProductID ANDs.SizeID= s_l.SizeID ANDco_l.ProductID= p.ProductID ANDco.ColourID= co_l.ColourID The first one uses JOINs and the second simply uses WHERE. As a matter of information, both have additional WHERE details added to refine the search. I'm using a fast PC, and there are only 14 products in the database (and not all that much data in the other tables). However, I was getting REALLY slow script execution, and I traced it to the SQL query. Running the first one takes an average of 7 seconds. Running the second query takes less than 1 second. It's almost instantaneous in fact. This kinda tells me NOT to use JOINs... and to stick with WHERE for this. But in that case, I am left confused as to where it is appropriate to use JOINs and where it isn't...? I did a couple of hours of Googling and didn't clear the matter up. All the articles I found pointed towards using JOINs. Obviously at the end of the day I'm going to use the faster method. Plus, after thinking about it, there's a lot more work being done with the JOINs, is there not...? I'd love to know what some other people think about this, and whether I'm just totally out on my JOIN usage or if other people are using them in the same situations. ::] krycek [::
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