I'm wondering if it's possible to accomplish this in MS Access 2007:
A client gave me several tables, and they asked me for some queries. One of them has to get a field value from a table, depending on the value of a field of each record. This means, depending on the region, it has to look at one table, a second, or a third one.
So, I was wondering if I could do something like this:
SELECT
table2.some_value
FROM
table1
INNER JOIN table2
ON CASE table1.SOME_VALUE THEN table3.id = table2.some_id ELSE
CASE table1.SOME_VALUE THEN table4.id = table2.some_id ELSE
table5.id = table2.some_id END END
Is it clear? IF not, just ask and I'll answer your doubts.
EDIT:
I think I was not clear enough. I have a several joins in my query, but I have this last one, in which its ON statement will be different, depending on the data. For example:
I have a record in a table that has a State field, with three possibilities: CA, TX, FL.
If the value is CA, the ON statement of that JOIN should be CA_Standard_table.field = myTable.field.
If it's TX, the ON statement of that JOIN should be TX_Standard_table.field = myTable.field
And the same logic goes for FL.
How can I accomplish that?
EDIT 2:
Here is the query code, the last JOIN is the one that matters for this. The three possibilities of tables to join with in the ON statement are:
EU_Accepted_Standards
CA_Accepted_Standards
NZ_Accepted_Standards
It will decide for one of them, depending of which of the following fields are checked:
CAStandard: it should take CA_Accepted_Standards.
EUSelStandard:it should take EU_Accepted_Standards.
NZ_Accepted_Standards: it should take NZ_Accepted_Standards
Query
SELECT
Projects.COMPAS_ID,
Projects.[Opportunity Name],
IIf([VolCap]=True,1) AS [Volume Cap],
IIf([DelGuarantee]=True,1) AS [Delivery Guarantee],
Projects.Tech_Level_Name,
Counterparty.CPExpertise,
Counterparty.CPFinStrength,
Geographic_Location.Country_RiskLevel,
Project_Stage_Risk.ProStaRiskLevel,
Counterparty.CPExperience,
Projects.Country_Name,
IIf([EU ETS]=True,1) AS EU,
IIf([CA ETS]=True,1) AS CA,
IIf([NZ ETS]=True,1) AS NZ,
IIf([Australia ETS]=True,1) AS Australia,
IIf([CAProjectType] is not null, CA_Accepted_Projects.CAPTRiskLevel,
IIf([EUSelProjType] is not null, EU_ETS_Standards.EUPTRiskLevel,
IIf([NZSelProjType] is not null, NZ_Accepted_Projects.NZPTRiskLevel))) as [Risk Level],
IIf([CAStandard] is not null, CA_Accepted_Standards.CAStanRiskLevel,
IIf([EUSelStandard] is not null, EU_Accepted_Standards.EUStanRiskLevel,
IIf([NZSelStandard] is not null, NZ_Accepted_Standards.NZStanRiskLevel))) as [Standard Risk]
FROM
Project_Stage_Risk
INNER JOIN (((((((((Counterparty
INNER JOIN Projects
ON Counterparty.CPID = Projects.[Counter Party])
INNER JOIN Geographic_Location
ON Projects.Country_Name = Geographic_Location.Country_Name)
left JOIN CA_Accepted_Projects
ON Projects.CAProjectType = CA_Accepted_Projects.CA_ProjectTypes)
left JOIN NZ_Accepted_Projects
ON Projects.NZSelProjType = NZ_Accepted_Projects.NZ_StandardID)
left JOIN EU_ETS_Standards
ON Projects.EUSelProjType = EU_ETS_Standards.EU_StandardID)
left JOIN CA_Accepted_Standards
ON Projects.CAStandard = CA_Accepted_Standards.ID)
left JOIN NZ_Accepted_Standards
ON Projects.NZSelStandard = NZ_Accepted_Standards.ID)
left JOIN EU_Accepted_Standards
ON Projects.EUSelStandard = EU_Accepted_Standards.ID)
left join Emissions_Trading_Systems
ON Emissions_Trading_Systems.ETS = EU_Accepted_Standards.ETS)
ON Project_Stage_Risk.ProStaID = Projects.[Project Stage];
cross join the two sets in a view, put the condition in the select. make 2 views of this view. Join the 2 views together.
You could create a UNION query that unions together the three tables you want to conditionally join to, including a "Some_Value" column that will contain the item on which you want to join. Essentially, for each table you include in the UNION, set the value of the "Some_Value" column to a value you can use in a where clause to differentiate things. Then create an overall query that joins (in your example, table2) to the union query and use a WHERE clause to limit the records to the ones you need. I have done similar things myself on projects in the past with great success.
Thanks for the answers. I know it was not well explained though, but in the end, I could solve this problem by writing a subquery.
Join all five tables together, and use that CASE expression inside the SELECT clause to choose the appropriate field from all tables.
SELECT
CASE table1.some_value
WHEN 'a' THEN table2.some_value
WHEN 'b' THEN table3.some_value
WHEN 'c' THEN table4.some_value
WHEN 'd' THEN table5.some_value
END
Related
Novice SQL Server
Can someone explain the logic of the below update with a join. I don't understand the setting of a specific value in the 'on' clause...
(#c is a tiny temp table with fields: cert, prod, cov, i)
update m
set inieff = i
from tmempt m
inner join #c on clntcode = '01208' and
polno = '00000408' and
certno = cert and
prodcode = prod and
covgcode = cov and
rcdsts = 'A'
...so how does '..on clntcode='01208' and polno='00000408'' work in the context of a join? I thought that joins work by field relationships...
Thanks
J
An inner join is simple. For each pair of rows in the two tables, the on clause is evaluated. When it evaluates to true (i.e. not false and not NULL), then the pair passes the filter.
Note that there is no specification whatsoever on the condition. The most typical conditions are equality conditions on one or more columns. However, inequalities, function calls, and even subqueries are allowed.
The definition of outer joins is just a slight variation on the inner join definition. For outer joins, rows are output from one or both tables even when the on clause does not evaluate to true.
For inner joins, putting conditions in the on versus where is really a matter of style. For outer joins, some conditions may need to go in the on -- and others in the where.
The join conditions can have whatever clauses you like.
The main purpose is to join one column of one table to a column in another table, but it can also be used to limit the rows you look at in the joined tables.
For example something like this is relatively common
select a1.address as postal, a2.address as street
from customer
join address a1 on a1.customerid=customer.id and a1.addresstype='postal'
join address a2 on a2.customerid=customer.id and a2.addresstype='street'
New to SQL but I want to be able to optimize my query by bringing just the right amount of data. I am doing a left join on CS Rep Name and WE, which are two columns present in both tables. I find that if I don't bring in CS Rep Name and WE in the TECDR table, the query would error. Is there a workaround to this? Since it is a left join, I don't need redundant data.
SELECT *
FROM Tish_Email_CSAT_Dump AS TECD
LEFT JOIN (SELECT CS_Rep_Name,
Team_Leader,
Operations_Manager,
Tenure,
WE,
FileName
FROM Tish_Email_CSAT_Dump_Roster) AS TECDR
ON TECD.CS_Rep_Name = TECDR.CS_Rep_Name
AND TECD.WE = TECDR.WE
When you embed a SELECT inside a query in place of a table, the result of a select (projection) behave like a table visible only inside the query.
In your case, the join is the same as if there were a table called TECDR with the columns that you select. Hence, if you leave out some columns of Tish_Email_CSAT_Dump_Roster from your SELECT, these columns would not be available for joining or selection.
However, in your case this is unnecessary: all you need to do is joining to the underlying table, like this:
SELECT
TECD.*
, TECDR.Team_Leader
, TECDR.Operations_Manager
, TECDR.Tenure
, TECDR.FileName
FROM Tish_Email_CSAT_Dump AS TECD
LEFT JOIN Tish_Email_CSAT_Dump_Roster AS TECDR
ON TECD.CS_Rep_Name = TECDR.CS_Rep_Name AND TECD.WE = TECDR.WE
select
<place the columns you want here>
from
Tish_Email_CSAT_Dump as TECD
Left join Tish_Email_CSAT_Dump_Roster as TECDR
On TECD.CS_Rep_Name = TECDR.CS_Rep_Name and TECD.WE = TECDR.WE
Hope the following helps or else please share the query that errors:
select TECD.Column1, TECD.Column2, TECDR.Column1, TECDR.Column2
from Tish_Email_CSAT_Dump as TECD
Left join Tish_Email_CSAT_Dump_Roster as TECDR
On TECD.CS_Rep_Name = TECDR.CS_Rep_Name and TECD.WE = TECDR.WE
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.
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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.
I need to retrieve all default settings from the settings table but also grab the character setting if exists for x character.
But this query is only retrieving those settings where character is = 1, not the default settings if the user havent setted anyone.
SELECT `settings`.*, `character_settings`.`value`
FROM (`settings`)
LEFT JOIN `character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
WHERE `character_settings`.`character_id` = '1'
So i should need something like this:
array(
'0' => array('somekey' => 'keyname', 'value' => 'thevalue'),
'1' => array('somekey2' => 'keyname2'),
'2' => array('somekey3' => 'keyname3')
)
Where key 1 and 2 are the default values when key 0 contains the default value with the character value.
The where clause is filtering away rows where the left join doesn't succeed. Move it to the join:
SELECT `settings`.*, `character_settings`.`value`
FROM `settings`
LEFT JOIN
`character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1'
When making OUTER JOINs (ANSI-89 or ANSI-92), filtration location matters because criteria specified in the ON clause is applied before the JOIN is made. Criteria against an OUTER JOINed table provided in the WHERE clause is applied after the JOIN is made. This can produce very different result sets. In comparison, it doesn't matter for INNER JOINs if the criteria is provided in the ON or WHERE clauses -- the result will be the same.
SELECT s.*,
cs.`value`
FROM SETTINGS s
LEFT JOIN CHARACTER_SETTINGS cs ON cs.setting_id = s.id
AND cs.character_id = 1
If I understand your question correctly you want records from the settings database if they don't have a join accross to the character_settings table or if that joined record has character_id = 1.
You should therefore do
SELECT `settings`.*, `character_settings`.`value`
FROM (`settings`)
LEFT OUTER JOIN `character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
WHERE `character_settings`.`character_id` = '1' OR
`character_settings`.character_id is NULL
You might find it easier to understand by using a simple subquery
SELECT `settings`.*, (
SELECT `value` FROM `character_settings`
WHERE `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1') AS cv_value
FROM `settings`
The subquery is allowed to return null, so you don't have to worry about JOIN/WHERE in the main query.
Sometimes, this works faster in MySQL, but compare it against the LEFT JOIN form to see what works best for you.
SELECT s.*, c.value
FROM settings s
LEFT JOIN character_settings c ON c.setting_id = s.id AND c.character_id = '1'
For this problem, as for many others involving non-trivial left joins such as left-joining on inner-joined tables, I find it convenient and somewhat more readable to split the query with a with clause. In your example,
with settings_for_char as (
select setting_id, value from character_settings where character_id = 1
)
select
settings.*,
settings_for_char.value
from
settings
left join settings_for_char on settings_for_char.setting_id = settings.id;
The way I finally understand the top answer is realising (following the Order Of Execution of the SQL query ) that the WHERE clause is applied to the joined table thereby filtering out rows that do not satisfy the WHERE condition from the joined (or output) table. However, moving the WHERE condition to the ON clause applies it to the individual tables prior to joining. This enables the left join to retain rows from the left table even though some column entries of those rows (entries from the right tables) do not satisfy the WHERE condition.
The result is correct based on the SQL statement. Left join returns all values from the right table, and only matching values from the left table.
ID and NAME columns are from the right side table, so are returned.
Score is from the left table, and 30 is returned, as this value relates to Name "Flow". The other Names are NULL as they do not relate to Name "Flow".
The below would return the result you were expecting:
SELECT a.*, b.Score
FROM #Table1 a
LEFT JOIN #Table2 b
ON a.ID = b.T1_ID
WHERE 1=1
AND a.Name = 'Flow'
The SQL applies a filter on the right hand table.
I have a query that shows me a listing of ALL opportunities in one query
I have a query that shows me a listing of EXCLUSION opportunities, ones we want to eliminate from the results
I need to produce a query that will take everything from the first query minus the second query...
SELECT DISTINCT qryMissedOpportunity_ALL_Clients.*
FROM qryMissedOpportunity_ALL_Clients INNER JOIN qryMissedOpportunity_Exclusions ON
([qryMissedOpportunity_ALL_Clients].[ClientID] <> [qryMissedOpportunity_Exclusions].[ClientID])
AND
([qryMissedOpportunity_Exclusions].[ClientID] <> [qryMissedOpportunity_Exclusions].[BillingCode])
The initial query works as intended and exclusions successfully lists all the hits, but I get the full listing when I query with the above which is obviously wrong. Any tips would be appreciated.
EDIT - Two originating queries
qryMissedOpportunity_ALL_Clients (1)
SELECT MissedOpportunities.MOID, PriceList.BillingCode, Client.ClientID, Client.ClientName, PriceList.WorkDescription, PriceList.UnitOfWork, MissedOpportunities.Qty, PriceList.CostPerUnit AS Our_PriceList_Cost, ([MissedOpportunities].[Qty]*[PriceList].[CostPerUnit]) AS At_Cost, MissedOpportunities.fBegin
FROM PriceList INNER JOIN (Client INNER JOIN MissedOpportunities ON Client.ClientID = MissedOpportunities.ClientID) ON PriceList.BillingCode = MissedOpportunities.BillingCode
WHERE (((MissedOpportunities.fBegin)=#10/1/2009#));
qryMissedOpportunity_Exclusions
SELECT qryMissedOpportunity_ALL_Clients.*, MissedOpportunity_Exclusions.Exclusion, MissedOpportunity_Exclusions.Comments
FROM qryMissedOpportunity_ALL_Clients INNER JOIN MissedOpportunity_Exclusions ON (qryMissedOpportunity_ALL_Clients.BillingCode = MissedOpportunity_Exclusions.BillingCode) AND (qryMissedOpportunity_ALL_Clients.ClientID = MissedOpportunity_Exclusions.ClientID)
WHERE (((MissedOpportunity_Exclusions.Exclusion)=True));
One group needs to see everything, the other needs to see things they havn't deamed as "valid" missed opportunity as in, we've seen it, verified why its there and don't need to bother critiquing it every single month.
Generally you can exclude a table by doing a left join and comparing against null:
SELECT t1.* FROM t1 LEFT JOIN t2 on t1.id = t2.id where t2.id is null;
Should be pretty easy to adopt this to your situation.
Looking at your query rewritten to use table aliases so I can read it...
SELECT DISTINCT c.*
FROM qryMissedOpportunity_ALL_Clients c
JOIN qryMissedOpportunity_Exclusions e
ON c.ClientID <> e.ClientID
AND e.ClientID <> e.BillingCode
This query will produce a cartesian product of sorts... each and every row in qryMissedOpportunity_ALL_Clients will match and join with every row in qryMissedOpportunity_Exclusions where ClientIDs do not match... Is this what you want?? Generally join conditions are based on a column in one table being equal to the value of a column in the other table... Joining where they are not equal is unusual ...
Second, the second iniquality in the join conditions is between columns in the same table (qryMissedOpportunity_Exclusions table) Are you sure this is what you want? If it is, it is not a join condition, it is a Where clause condition...
Second, your question mentions two queries, but there is only the one query (above) in yr question. Where is the second one?