I have some information where the IdNumbers (not primary key Ids, just random Ids assigned to individuals) are not always correct in my first table.
Therefore I am joining my second table on both Ids and names, and trying to get it to where it will join on names only if the IdNumbers do not match.
I'm working on a query with a join statement that is roughly as follows (I'm leaving out the SELECT, WHERE, and ORDER BY sections because I believe that they are not having an effect on this issue and I don't want to be confusing, as they are stupidly complex - if the portion of the query below should be working like I want it to and the problem is obviously somewhere else, then just tell me so and that will answer my question):
FROM Table1
FULL OUTER JOIN Table2 ON ((Table1.IdNumber = Table2.IdNumber)
OR (Table1.IdNumber != Table2.IdNumber
AND Table1.Lname = Table2.Lname
AND Table1.Fname = Table2.Fname))
However, it is joining the people who have both matching Ids and matching names multiple times like so:
Fname M Lname Table1.IdNumber Table2.IdNumber2
Matthew - Smith 1 2
Matthew H Smith 2 1
Matthew - Smith 1 1
Matthew H Smith 2 2
So it is pulling the last 2 because their ids match, but also joining the first 2 because their ids do not match and their names match, but why is it even joining the first 2 to begin with? I suspect that it ignores the != statement when deciding where to join since the other conditions are fulfilled, but I'd like it to take this != statement into account somehow.
If this should be working, like I said before, just tell me and it will answer my question.
(*EDIT)
Sorry, I should have named these properly - I've revised the names. And the full outer join is necessary, I need everything from both tables no matter what and it's working fine, but thank you for the suggestion.
Given how messy this would be to do in one JOIN, I would suggest using a temp table to hold the relationships.
You can insert all of your IDs from the into first table into a temp table, then do two passes to update a column holding the 2nd table ID - first using where the ID matches, and second where the ID doesn't match but the name does.
You can then use this table to join the two tables, retrieving up to one record from table 2 for each record in table 1.
I think you want something like this:
select t1.*,t2.*
from t1,t2
where t1.id = t2.id
and t1.name = t2.name
union
select t1.*,t2.*
from t1,t2
where t1.id ! t2.id
Your query should work, if the columns are coming from the right tables. Because you are not using table aliases, I suspect that you have an expression such as:
fname1 = fname2
and both columns are in the same table. Or worse:
fname1 = fname1
which is essentially always TRUE (except when fname1 is not null).
Your query might work, but it will be inefficient in most databases, because they will use nested loop optimizations. Consider rewriting the query to be:
from table1 t1 full outer join
table2 byID
on t1.IdNumber = byID.IdNumber full outer join
table2 byName
on t1.fname = byName.fname and t1.lname = byName.lname and t1.idNumber <> byName.idNumber
This will require changing other clauses in your query, typically to something like:
coalesce(byId.column, byName.column) as Column
Related
I have two separate data tables.
This is Table1:
Customer Name Address 1 City State Zip
ACME COMPANY 1 Street Road Maspeth NY 11777
This is Table2:
Customer Active Account New Contact
ACME Y John Smith
I am running a query using the JOIN where only include rows where the joined fields from both tables are equal.
I am joining Customer Name from Table1 and Customer from Table2. Obviously no match. What I am trying to do is show results where the first 4 characters match in each table so I get a result or match. Is this possible using LIKE or LEFT?
Yes, that's possible.
But I doubt, that every name in table 2 only has 4 letters, so here's a solution where the name in table2 is the beginning of the name in table1.
Concat the string with a %. It's a placeholder/wildcard for "anything or nothing".
SELECT
*
FROM
Table1
INNER JOIN Table2 ON Table1.CustomerName LIKE CONCAT(Table2.Customer, '%');
Concatenating of strings may work differently between DBMS.
It probably is, though this might depend on the Database you are using. For example, in Microsoft SQL, it would work to use somthing like this:
SELECT *
FROM [Table1] INNER JOIN [Table2]
ON LEFT([Table1].[Customer Name],4) = LEFT([Table2].[Customer],4)
Syntax may be different if using other RDBMS. What are you trying this on?
Seems like this should work:
Select *
From Table1, Table2
Where Table1.CustomerName Like Cat('%',Trim(Table2.CustomerName),'%')
If you are only trying to match first four Characters you can use following :
SELECT --your columns
FROM Table1 T1
JOIN Table T2
ON
SUBSTRING ( T1.CustomerName ,1, 4) = SUBSTRING ( T2.Customer ,1, 4)
I have 2 tables in a MYSQL database wich look like this:
Klant:
ID Naam Email Soort Status
6 test test test2
7 status test test test 20
8 soort test test test
9 soort test 2 test2 Museum
Mail:
ID Content Datum Titel
1 (lots of encoded HTML) 18-03-13 test
2 (lots of encoded HTML) 18-03-13 test2
4 (lots of encoded HTML) 18-03-13 alles weer testen
(yes, I'm still testing alot^^)
Now I have a SQL query that selects all from 'Klant' with a where clause which gets the ID from a previous page:
$strSQL = "SELECT * FROM Klant WHERE ID = '".$_GET["ID"]."' ";
What I want is to JOIN this query with the following query:
SELECT ID, Titel FROM Mail;
EDIT:
From all your answers and comments I think I begin to think my question maybe is totally wrong.. I'll explain where I need it for and I might not even need JOIN? I currently have a table wich includes the data from 'Klant' which looks like this:
The meaning is that I add another table which includes all the ID's and Title's from 'Mail'. I am sorry for the confusion I may have caused with you since I wasn't that clear with my question. I hope that this may clear up what I want and you guys can maybe tell me if I even need to JOIN this or can I do something else?
I am still a student and this is the first time I've had to use JOIN and I can't figure this out. If anyone can show me how to do this or push me in the right direction it would be great!
SELECT * FROM Klant t1
JOIN
SELECT ID, Titel FROM Mail t2
ON t1.ID = t2.ID
WHERE t1.Name = 'test'
To have the desired result do the following:
SELECT * FROM Klant t1
JOIN
SELECT ID, Titel FROM Mail t2
ON t1.ID = t2.ID
And if you want to have a specific row than just add the where clause:
WHERE t1.ID = 6
or
WHERE t1.Naam = 'test'
and so on
It is difficult to see how a JOIN is applicable in the example in your question.
A JOIN let's you pull information from more than one table based on a relationship. As far as I can see, your table's don't have any way to link a row in one with a row in the other, unless SteveP is correct and your id's provide that relationship.
For example, if your klant table had a mail_id column then you could do
SELECT *
FROM klant
JOIN mail ON klant.mail_id = mail.id
and this would return a row for every matching pair of rows in the two tables. Alternatively you could use a LEFT OUTER JOIN to pull back all rows from the table on the left of the JOIN and optionally data from a matching row on the right.
If there is nothing joining the table, you can use a CROSS JOIN which will return you a full cartesian of each row in table1 with every row in table2.
Something people often confuse with a JOIN is a UNION which allows you to write 2 SELECT statements and return the result set of both combined/joined together, but these should return the same columns in each query (e.g. selecting NULL in place of the column in a query if the query doesn't pull data for that column)
I'm guess that you want to join on the ID field which is common between the tables.
select * from Klant, Mail where Klant.ID = '".$_GET["ID"]."' and Klant.ID = Mail.ID
You can also do
select * from Klant
join Mail on Mail.ID = Klant.ID
where Klant.ID = '".$_GET["ID"]."'
You can do this directly by using the following query :
select k.ID,k.Naam, k.Email,k.Soort,k.Status, m.ID,m.Titel from Klant k, Mail m where k.ID = m.ID and k.ID = '".$_GET["ID"]."'
This marks the first time I ask a question on stack overflow, and probably the 5000th time i've visited the site. So first off, thanks for all your hard work!
So I have a basic select query on a single table that returns two rows of similar data and are linked via a shared PK.
I want to retrieve all fields from the first row, and only one of the columns from the second under an alias.
Basically flattening the two records into one but only using one of the columns from the second row.
OK Here is a screenshot.
http://www.flickr.com/photos/imagevault/8581053528/
Looking at the first results window I want the Second "Comp" value to show up as an additional column on the first row as a "RentalComp". IF there is only one row returned for a given propertyid then it can just be null.
Thanks!
.. I'm at a loss of what to google for so here i am.
SELECT a.*, b.Comp AS RentalComp
FROM dbo.vwComps AS a LEFT OUTER JOIN dbo.vwComps AS b ON a.PropertyID = b.PropertyID
AND b.ConfigurationUsed = 2
WHERE (a.ConfigurationUsed = 1)
The key was specifying multiple conditions in the 'ON' statement. THen doing a basic filter in the where clause.
I kept trying to do everything in the where an it was filtering everything out.
Is this what you're looking for?
SELECT t1.*,
t2.col
FROM table1 t1
JOIN table2 t2
ON t1.key = t2.key
I need to flatten out 2 rows in a vertical table (and then join to a third table) I generally do this by making a derived table for each field I need. There's only two fields, I figure this isn't that unreasonable.
But I know that the rows I want back in the derived table, are the subset that's in my join with my third table.
So I'm trying to figure out the best derived tables to make so that the query runs most efficiently.
I figure the more restrictive I make the derived table's where clause, the smaller the derived table will be, the better response I'll get.
Really what I want is to correlate the where clause of the derived table with the join with the 3rd table, but you can't do that in sql, which is too bad. But I'm no sql master, maybe there's some trick I don't know about.
The other option is just to make the derived table(s) with no where clause and it just ends up joining the entire table twice (once for each field), and when I do my join against them the join filters every thing out.
So really what I'm asking I guess is what's the best way to make a derived table where I know pretty much specifically what rows I want, but sql won't let me get at them.
An example:
table1
------
id tag value
-- ----- -----
1 first john
1 last smith
2 first sally
2 last smithers
table2
------
id occupation
-- ----------
1 carpenter
2 homemaker
select table2.occupation, firsttable.first, lasttable.last from
table2, (select value as first from table1 where tag = 'first') firsttable,
(select value as last from table1 where tag = 'last') lasttable
where table2.id = firsttable.id and table2.id = lasttable.id
What I want to do is make the firsttable where clause where tag='first' and id = table2.id
DERIVED tables are not to store the intermediate results as you expect. These are just a way to make code simpler. Using derived table doesnt mean that the derived table expression will be executed first and output of that will be used to join with remaining tables.Optimizer will automaticaly faltten derived tables in most of the cases.
However,There are cases where the optimizer might want to store the results of the subquery and thus materilize instead of flattening.It usually happens when you have some kind of aggregate functions or like that.But in your case the query is too simple and thus optimizer will flatten query
Also,storing derived table expression wont make your query fast it will in turn could make it worse.Your real problem is too much normalization.Fix that query will be just a join of two tables.
Why you have this kind of normalization?Why you are storing col values as rows.Try to denormalize table1 so that it has two columns first and last.That will be best solution for this.
Also, do you have proper indexes on id and tag column? if yes then a merge join is quite good for your query.
Please provide index details on these tables and the plan generated by your query.
Your query will be used like an inner join query.
select table2.occupation, first.valkue as first, last.value as last
from
table2
inner join table1 first
on first.tag = 'first'
and first.id =table2.id
inner join table1 last
on last.tag = 'last'
and table2.id = last.id
I think what you're asking for is a COMMON TABLE EXPRESSION. If your platform doesn't implement them, then a temporary table may be the best alternative.
I'm a little confused. Your query looks okay . . . although it looks better with proper join syntax.
select table2.occupation, firsttable.first, lasttable.last
from table2 join
(select value as first from table1 where tag = 'first') firsttable
on table2.id = firsttable.id join
(select value as last from table1 where tag = 'last') lasttable
on table2.id = lasttable.id
This query does what you are asking it to do. SQL is a declarative language, not a procedural language. This means that you describe the result set and rely on the database SQL compiler to turn it into the right set of commands. (That said, sometimes how a query is structured does make it easier or harder for some engines to produce efficient query plans.)
I'm aware that this question's title might be a little bit inaccurate but I couldn't come up with anything better. Sorry.
I have to fetch 2 different fields, one is always there, the other isn't. That means I'm looking at a LEFT JOIN. Good so far.
But the row I want shown is not the row whose existence is uncertain.
I would like to do something like:
Show name and picture, but only show the picture if that name has a picture_id. Otherwise show nothing for the picture, but I still want the names regardless(left join).
I know this might be a little confusing but there's some clever guys out here so I guess somebody will understand it.
I tried some approaches but I couldn't quite say what I want in SQL.
P.S.: solutions specific to Oracle are good too.
------------------------------------------------------------------------------------------------------------------------------------
EDIT I've tried some queries but the main problem I found is that, inside the ON clause, I am only able to reference the last table mentioned, in other words:
There are four tables from which I'm retrieving data, but I can only mention the last (third table) inside the on clause of the LEFT JOIN(which is the 4th table). I'll describe the tables hopefully that'll help. Try not to delve too much on the names, because they are in Portuguese:
There are 4 tables. The fields I want to retrieve are :TB395.dsclaudo and TB397.dscrecomendacao, for a given TB392.nronip. The tables are as follows:
TB392(laudoid,nronip,codlaudo) // laudoid is PK, references TB395
TB395(codlaudo,dsclaudo) //codlaudo is PK
TB398(laudoid,codrecomendacao) //the pair laudoid,codrecomendacao is PK , references TB397
TB397(codrecomendacao,dscrecomendacao) // codrecomendacao is PK
Fields with the same name are foreign keys.
The problem is that there's no guarantee that, for a given laudoid,there will be one codrecomendacao. But, if there is, I want the dscrecomendacao field returned, that's what I don't know how to do. But even if there isn't a corresponding codrecomendacao for the laudoid, I still want the dsclaudo field, that's why I think a LEFT JOIN applies.
Sounds like you want your primary row source to be the join of TB392 and TB395; then you want an outer join to TB398, and when that gets a match, you want to lookup the corresponding value in TB397.
I would suggest coding the primary join as one inline view; the join between the two extra tables as a second inline view; and then doing an outer join between them. Something like:
SELECT ... FROM
(SELECT ... FROM TB392 JOIN TB395 ON ...) join1
LEFT JOIN
(SELECT ... FROM TB398 JOIN TB397 ON ...) join2
ON ...
It would be nice if you could specify what your tables are, which columns are on which tables, and what columns they join on. Its not clear if you have two tables or only one. I guess you have two tables because you are talking about a LEFT JOIN, and seem to imply that the join is on the name column. So you can use the NVL2 function to accomplish waht you want. So guessing what I can from your question, maybe something like:
SELECT T1.name
, NVL2( T2.picture_id, T1.picture, NULL )
FROM table1 T1
LEFT JOIN
table2 T2
ON T1.name = T2.name
If you only have one table, then its even simpler
SELECT T1.name
, NVL2( T1.picture_id, T1.picture, NULL )
FROM table1 T1
I think you need:
SELECT ...
FROM
TB395
JOIN
TB392
ON ...
LEFT JOIN --- this should be a LEFT JOIN
TB398
ON ...
LEFT JOIN --- and this as well, so the previous is not cancelled
TB397
ON ...
The details may be not accurate:
SELECT
a.dsclaudo
, b.laudoid
, c.codrecomendacao
, d.dscrecomendacao
FROM
TB395 a
JOIN
TB392 b
ON b.codlaudo = a.codlaudo
LEFT JOIN
TB398 c
ON c.laudoid = b.laudoid
LEFT JOIN
TB397 d
ON d.codrecomendacao = c.codrecomendacao
Create two views and then do your left join on the views. For example:
Create View view392_395
as
SELECT
t1.laudoid,
t1.nronip,
t1.codlaudo,
t2.dsclaudo
FROM TB392 t1
INNER JOIN TB395 t2
ON t1.codlaudo
= t2.codlaudo
Create View view398_397
as
SELECT
t1.laudoid,
t1.codrecomendacao,
t2.dscrecomendacao
FROM TB398 t1
INNER JOIN TB397 t2
ON t1.codrecomendacao
= t2.codrecomendacao
SELECT
v1.laudoid,
v1.nronip,
v1.codlaudo,
v1.dsclaudo,
v2.codrecomendacao,
v2.dscrecomendacao
FROM view392_395 v1
LEFT OUTER JOIN view398_397 v2
ON v1.laudoid
= v2.laudoid
In my opinion, views are always under used. Views are your friend. They can simplify some of the most complicated queries.