I'm asking if is it possible to use join with 2 clauses of differente tables like :
select t1.x,t1.y, t1.z
from t1
inner join t2 on t1.conditionA = t2.conditionA
inner join t3 on t2.conditionB = t3.conditionB
inner join t4 on t3.conditionC = t4.conditionC and t2.conditionD = t4.conditionD
where....
Is it worng? how should I do it?
Yes, you can, but it is a clue that your tables are not well designed.
Related
I'm trying to rewrite the following query which was generated in some part by Impromptu. For some reason I cannot get my head around the multiple tables after the FROM and the nest of joins that follows. I have always used a "master" table then joined anything I would need after that. i.e select from, left join (table) on x=x left join (table) on x=x and so on.
I'm having a difficult time with the parenths etc... in this. What would it look like written in "normal" query style? Thanks so much in advance!
select
T6."dateofservice"
, getdate(), -20000 - (1 - convert(float(53),-2) / abs(-2)) / 2
, T1."pgrp_specialty"
, T1."pgrp_prov_combo"
, T2."patsex"
, T3."restricted"
, T2."patdob"
, T2."patdecdate"
, T2."acctno"
, T2."patno"
from
"acctdemo_t" T3, "transaction_t" T5,
("patdemo_t" T2
LEFT OUTER JOIN ("provcode_t" T8
LEFT OUTER JOIN "provalt_t" T1 on T8."px" = T1."accesspractice" and T8."provcode" = T1."accessprovidercode") on T2."provcode" = T8."provcode")
LEFT OUTER JOIN "insset_t" T4 on T2."acctno" = T4."acctno" and T2."patno" = T4."patno", "charge_t" T6
LEFT OUTER JOIN "poscode_t" T7 on T6."poscode" = T7."poscode"
where
T2."patsex" <> 'U'
and T7."posid" = '3'
and T6."correction" = 'N'
and T5."txtype" = 'C'
and (T4."defaultset" = 'Y' or
(T4."inssetno" = 0 or T4."inssetno" is null)
and T4."defaultset" is null)
and T6."chgno" = T5."chgno"
and T2."patno" = T6."patno"
and T2."acctno" = T6."acctno"
and T2."acctno" = T3."acctno"
SQL written with multiple tables, separated by comma is implied INNER JOIN, with the where clause serving as the join clause. For example,
select * from table1 a, table2 b
where a.id = b.id
is the same as:
select * from table1 a inner join table2 b on a.id = b.id
So, in your case, this part:
from "acctdemo_t" T3
, "transaction_t" T5
is implying inner join between acctdemo_t and transaction_t.
And - the third part of this:
("patdemo_t" T2 LEFT OUTER JOIN
("provcode_t" T8 LEFT OUTER JOIN "provalt_t" T1 on T8."px" = T1."accesspractice" and T8."provcode" = T1."accessprovidercode")
on T2."provcode" = T8."provcode")
Is actually a tableset being created on the fly with its own clauses, and is basically acting as a table in this join. Also being joined with Inner join, since its added with a comma.
I believe this can definitely written to be more readable, and the inline tableset being created isn't going to be good for performance, but that totally depends on the number of records you have.
I have a query in sqlserver that needs to be translated to sqlite3, but this query uses "Right outer join", the problem is that sqlite doesn't support this operator yet.
how can I translate this query to use only "left outer join" instead of "right" outer join?
SELECT *
FROM P RIGHT OUTER JOIN
CL RIGHT OUTER JOIN
C LEFT OUTER JOIN
CC ON C.IDC = CC.RIDC ON
C.IDC = C.RIDCL ON P.IDP = C.RIDP
Thanks.
PS: I'm having trouble also with the sqlite joins precedence and associativity, don't know how it may alter the final result by reordering the tables.
In this query, the table c is in the middle. So that is driving the query.
Your on conditions are in strange places. I am guessing this is what you mean:
SELECT *
FROM C LEFT OUTER JOIN
CC
ON C.IDC = CC.RIDC LEFT OUTER JOIN
P
ON P.IDP = C.RIDP LEFT OUTER JOIN
CL
ON CL.IDC = C.RIDCL
An additional remark on the join syntax.
Most people write
Tab1 JOIN Tab2 ON ... JOIN Tab3 ON ... JOIN Tab4 ON ...
probably because this is the "natural" way, one table after the other.
But your joins use the "other" syntax i usually try to avoid.
Tab1 JOIN Tab2 JOIN Tab3 JOIN Tab4 ON ... ON ... ON ...
Logically joins are processed in the order of ON, so adding parens results in:
( P
RIGHT OUTER JOIN
( CL
RIGHT OUTER JOIN
( C
LEFT OUTER JOIN
CC
ON C.IDC = CC.RIDC
) p
ON C.IDC = C.RIDCL
)
ON P.IDP = C.RIDP
)
Rewriting it results in a join order C-CC-CL-P. This is not the C-CC-P-CL order Gordon used, but in your case this doesn't matter, because C is the main table :-)
Can sombody Explains me about joins?
Inner join selects common data based on where condition.
Left outer join selects all data from left irrespective of common but takes common data from right table and vice versa for Right outer.
I know the basics but question stays when it comes to join for than 5, 8, 10 tables.
Suppose I have 10 tables to join. If I have inner join with the first 5 tables and now try to apply a left join with the 6th table, now how the query will work?
I mean to say now the result set of first 5 tables will be taken as left table and the 6th one will be considerded as Right table? Or only Fifth table will be considered as left and 6th as right? Please help me regarding this.
When joining multiple tables the output of each join logically forms a virtual table that goes into the next join.
So in the example in your question the composite result of joining the first 5 tables would be treated as the left hand table.
See Itzik Ben-Gan's Logical Query Processing Poster for more about this.
The virtual tables involved in the joins can be controlled by positioning the ON clause. For example
SELECT *
FROM T1
INNER JOIN T2
ON T2.C = T1.C
INNER JOIN T3
LEFT JOIN T4
ON T4.C = T3.C
ON T3.C = T2.C
is equivalent to (T1 Inner Join T2) Inner Join (T3 Left Join T4)
It's helpful to think of JOIN's in sequence, so the former is correct.
SELECT *
FROM a
INNER JOIN b ON b.a = a.id
INNER JOIN c ON c.b = b.id
LEFT JOIN d ON d.c = c.id
LEFT JOIN e ON e.d = d.id
Would be all the fields from a and b and c where all the ON criteria match, plus the values from d where its criteria match plus all the contents of e where all its criteria match.
I know RIGHT JOIN is perfectly acceptable, but I've found in my experience that it's unnecessary - I almost always just join things from left to right.
> Simple INNER JOIN VIEW code...
CREATE VIEW room_view
AS SELECT a.*,b.*
FROM j4_booking a INNER JOIN j4_scheduling b
on a.room_id = b.room_id;
You can apply join like this..
select a.*,b.*,c.*,d.*,e.*
from [DatabaseName].[Table_a] a
INNER JOIN [DatabaseName].[Table_b] b ON a.id = b.id
INNER JOIN [DatabaseName].[Table_c] c ON b.id=c.id
INNER JOIN [DatabaseName].[Table_d] d on c.id=d.id
INNER JOIN [DatabaseName].[Table_e] e on d.id=e.id where a.con=5 and
b.con=6
Here, at place of a.* and in where condition, you can show column(filed) which you like and according condition in where condition. You can insert more table and database as per your choice. But mind that you need to mention database name and alias if you work in different database.
Just tried the following from the Example DataBase given in W3School. Worked Fine for me.
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate, Products.ProductName, Products.ProductID
FROM Orders
INNER JOIN Products
INNER JOIN Customers
ON Orders.CustomerID=Customers.CustomerID;
Join used to combine rows from two or more tables, based on a related column between them. This example from Adventure works:
SELECT a.[EmailAddress],b.[FirstName],b.[LastName],c.[PhoneNumber],d.[Name]
FROM [Person].[EmailAddress] a
INNER JOIN [Person].[Person] b
ON a.BusinessEntityID = b.BusinessEntityID
INNER JOIN [Person].[PersonPhone] c
ON b.BusinessEntityID = c.BusinessEntityID
INNER JOIN [Person].[PhoneNumberType] d
ON c.phoneNumberTypeID = d.phoneNumberTypeID
I am new to sql and I am trying to join 4 tables together but just cant get the hang of it.
I am trying to do this with an inner join but I always get an syntax error with access.
SELECT *
from kdst,aufpos
inner join( artst inner join vert on kdst.vertreter = vert.vertnr)
on aufpos.artnr = artst.artnr;
This is my code but it does not work. I dont know what to do anymore, I hope someone can help me.
Build using the query design window
Then switch to sql view
Select *
From table1 t1
Inner join table2 t2 on t1.id = t2.fkid
Inner join table3 t3 on t1.id = t3.fkid
...
This is if you want to join multiple tables to the same parent table (table1). Fkid is the column of the foreign key field that refers to the primary key of the parent table.
I've "inherited" a well over 10-year old app, and it does show its age at times. I've stumbled across a really weird view definition today - I just can't seem to make sense of it! Can you help me? This was originally on SQL Server 7.0 and has since been migrated to SQL Server 2005 - but obviously it's never been refactored / redone....
This is the view definition - based on a bunch of tables and another view:
CREATE VIEW dbo.MyOddView
AS
SELECT
t1.MVOID, t1.SomeOtherColumn,
t2.Number ,
t3.OID, t3.FKOID,
t4.AcctNo,
t5.ShortDesc, t5.ZipCode, t5.City,
t6.BankAcctNo
FROM
dbo.viewFirst vf
INNER JOIN
dbo.Table1 t1 ON vf.MVOID = t1.MVOID AND vf.ValidFrom = t1.ValidFrom
LEFT OUTER JOIN
dbo.Table2 t2
RIGHT OUTER JOIN
dbo.Table3 t3 ON t2.OID = t3.FKOID
LEFT OUTER JOIN
dbo.Table4 t4 ON t3.ZVOID = t4.OID
LEFT OUTER JOIN
dbo.Table5 t5
INNER JOIN
dbo.Table4 t6 ON t5.OID = t6.BCOID
ON t4.ZVOID = t5.OID
ON t2.AddressOID = t4.OID
GO
What I don't get are the two JOIN's (for Table2 t2 and Table5 t5) which have no JOIN condition listed next to them, and the two extra ON conditions at the end of the view definition - I can't seem to rip this apart and put it back together in "proper" ANSI JOIN syntax so that my row count is the same...... (my original view gets me something over 12'000 rows, and a first attempt at refactoring this returned a single row......)
Any ideas? What the heck is this? Seems like totally invalid SQL to me - but it appears to be doing its job (and has been for the past several years....) Any thoughts? Pointers?
SELECT ...
FROM dbo.viewFirst vf
INNER JOIN dbo.Table1 t1
ON vf.MVOID = t1.MVOID
AND vf.ValidFrom = t1.ValidFrom
LEFT OUTER JOIN dbo.Table2 t2
RIGHT OUTER JOIN dbo.Table3 t3
ON t2.OID = t3.FKOID
LEFT OUTER JOIN dbo.Table4 t4
ON t3.ZVOID = t4.OID
LEFT OUTER JOIN dbo.Table5 t5
INNER JOIN dbo.Table4 t6
ON t5.OID = t6.BCOID
ON t4.ZVOID = t5.OID
ON t2.AddressOID = t4.OID
This syntax is covered in chapter 7 of Inside SQL Server 2008 T-SQL Querying or see this article by Itzik Ben Gan and the follow up letter by Lubor Kollar
Having the ON clause for t2.AddressOID = t4.OID last for example means that the JOIN of t2 logically happens last. i.e the other joins are logically processed first then the LEFT JOIN happens against the result of those Joins.