i have a query which is used to generate reports. There are multiple fields to be displayed. One requirement is such that i need to join one table to different tables with different aliases for data. e.g., table 1 employee id with employee table for knowing the full name. similarly table 2 employee id with employee table for table 2 employee id full name. PFB the query:
select * from office o
left join employee e
on e.id=o.id
left join master m
on m.id=o.id
left join student s1
on e.id=s1.id
left join student s2
on m.id=s2.id
Can we optimize this query to use only one join statement of student table instead of multiple table join statement? I need to reduce the number of tables used in the query since i'm getting the error as too many tables in the query maximum allowed is 50. Please help. Appreciate.
Can we optimize this query to use only one join statement of student
table instead of multiple table join statement?
No, I would not call it query optimization. However, for reporting purposes you reduce the joins by creating views.
http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc00801.1510/html/iqrefso/X315714.htm
Related
I have two tables, one table bill, and one table log.
Each bill has one log. Therefore there is a third table bill_log with two columns bill_id and log_id.
I want to select all columns from bill and logs in one statement with
bill_log.bill_id=bill.id and bill_log.log_id=log.id
I tried to join these tables, but it didn't work. Can anyone help?
select bill.*,log.* from bill
inner join bill_log on bill_log.bill_id=bill.id
inner join log on bill_log.log_id=log.id
I have a requirement below.
Now I have to get output like below
How can this be achieved ?
I have written the below SQL but parent_position_id is coming, not parent_position_code
select
hapf.position_code,
pphf.parent_position_id
from
hr_all_positions_f hapf, PER_POSITION_HIERARCHY_F pphf
where
hapf.position_id = pphf.position_id
Should I write a sub query? How should I proceed ?
This is Oracle SQL
Thanks,
Shivam
Noone ever said you could only join a table in once:
select
chi.position_code,
par.position_code as parent_position_code
from
hr_all_positions_f hapf
INNER JOIN PER_POSITION_HIERARCHY_F chi on hapf.position_id = chi.position_id
INNER JOIN PER_POSITION_HIERARCHY_F par on hapf.parent_position_id = par.position_id
Bear it in mind; I see people coming to thinking all the time that they can only join a table once. If one table decodes a value in 3 different columns, then you sure can join that same table in 3 times... Imagine if it were an address table, and a Student had a HomeAddressId, WorkAddressId and StudyAddressId, and the Address table held all these addresses - you'd join the addresses table to the Student table 3 times to get all the data..
I create a new view in SQL Server 2008 from two tables that have relation on a field. I want to create a report and do grouping on that common field.
For example:
table1: student(ID,first-name,last-name,phone,address,...)
table2: courses(ID,fk_ID,Course,....)
Now I want to have report that shows all data from both tables with grouping on ID from student table, that must show courses information separated for every student.
my query is:
SELECT TOP (100) PERCENT
dbo.tbl_student.ID,
dbo.tbl_student.firstname, dbo.tbl_student.lastname,
dbo.tbl_courses.Coursename,
dbo.tbl_Courses.CourseDate, dbo.tbl_courses.coursetype,
FROM
dbo.tbl_student LEFT OUTER JOIN
dbo.tbl_courses ON dbo.tbl_student.ID = dbo.tbl_courses.fk_id
ORDER BY
dbo.tbl_student.firstname DESC
But when I create a new report from this view, it shows just one record for every group. I spent 2 hours to solve the problem but I did not succeed.
please help me to create report from two or more tables.
Now it shows one record duplicates for several times for every group
Have you tried a query like this:
SELECT s.[ID], s.[first-name], s.[last-name], s.[phone], ...
c.[ID], c.[Course], ...
FROM student s
LEFT OUTER JOIN
courses c ON s.[ID] = c.[fk_ID]
Hi I have an SQL table which has two tables which make reference to the same foreign key in a separate table twice... something like
SALES table
idSales idClient1 idClient2
1 1 2
CLIENT table
idClient ClientName
1 Bob
2 Mick
I want to join the SALES table to the CLIENT table and return data as follows:
idSales idClientClientName1 idClientClientName2
1 Bob Mick
Can anyone help with the SQL for this? I'm getting ambiguous column name errors on my join.
Thank you
You need to basically join table Client on table Sales twice because there are two columns on table Sales that are dependent on table Client.
SELECT a.idSales,
b.ClientName ClientName1,
c.ClientName ClientName2
FROM Sales a
INNER JOIN Client b
ON a.idClient1 = b.idClient
INNER JOIN Client c
ON a.idClient2 = c.idClient
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
But when one of the columns or both columns are nullable, INNER JOIN will not give you all records from Sales because it will only select where it has atleast one match on the other table. Instead use LEFT JOIN.
I might add that in cases like this, I use table aliases that hint at what entity you are linking to in the joined table. If for example, the foreign keys were to an address table, and you had a work address, and a Home address, I would use tables aliases of h and w for the two joins. In your case, i.e.,
Selext s.idSales,
c1.ClientName ClientName1,
c2.ClientName ClientName2
From Sales s
Join Client c1
On c1.idClient = s.idClient1
Join Client c2
On c2.idClient = s.idClient2
For those beginner SQL folks who may see this question in the future, it's helpful to add in the AS words, it makes it clearer still:
SELECT
Sale.idSales,
c1.ClientName AS ClientName1,
c2.ClientName AS ClientName2
FROM
Sales AS Sale
INNER JOIN Client AS c1 ON Sale.idClient1 = c1.idClient
INNER JOIN Client AS c2 ON Sale.idClient2 = c2.idClient
I have a database with two tables
One with games
and one with participants
A game is able to have more participants and these are in a different table.
Is there a way to combine these two into one query?
Thanks
You can combine them using the JOIN operator.
Something like
SELECT *
FROM games g
INNER JOIN participants p ON p.gameid = g.gameid
Explanation on JOIN operators
INNER JOIN - Match rows between the two tables specified in the INNER
JOIN statement based on one or more
columns having matching data.
Preferably the join is based on
referential integrity enforcing the
relationship between the tables to
ensure data integrity.
o Just to add a little commentary to the basic definitions
above, in general the INNER JOIN
option is considered to be the most
common join needed in applications
and/or queries. Although that is the
case in some environments, it is
really dependent on the database
design, referential integrity and data
needed for the application. As such,
please take the time to understand the
data being requested then select the
proper join option.
o Although most join logic is based on matching values between
the two columns specified, it is
possible to also include logic using
greater than, less than, not equals,
etc.
LEFT OUTER JOIN - Based on the two tables specified in the join
clause, all data is returned from the
left table. On the right table, the
matching data is returned in addition
to NULL values where a record exists
in the left table, but not in the
right table.
o Another item to keep in mind is that the LEFT and RIGHT OUTER
JOIN logic is opposite of one another.
So you can change either the order of
the tables in the specific join
statement or change the JOIN from left
to right or vice versa and get the
same results.
RIGHT OUTER JOIN - Based on the two tables specified in the join
clause, all data is returned from the
right table. On the left table, the
matching data is returned in addition
to NULL values where a record exists
in the right table but not in the left
table.
Self -Join - In this circumstance, the same table is
specified twice with two different
aliases in order to match the data
within the same table.
CROSS JOIN - Based on the two tables specified in the join clause, a
Cartesian product is created if a
WHERE clause does filter the rows.
The size of the Cartesian product is
based on multiplying the number of
rows from the left table by the number
of rows in the right table. Please
heed caution when using a CROSS JOIN.
FULL JOIN - Based on the two tables specified in the join clause,
all data is returned from both tables
regardless of matching data.
example
table Game has columns (gameName, gameID)
table Participant has columns (participantID, participantName, gameID)
the GameID column is the "link" between the 2 tables. you need a common column you can join between 2 tables.
SELECT gameName, participantName
FROM Game g
JOIN Participat p ON g.gameID = p.gameID
This will return a data set of all games and the participants for those games.
The list of games will be redundant unless you structure it some other way due to multiple participants to that game.
sample data
WOW Bob
WOW Jake
StarCraft2 Neal
Warcraft3 James
Warcraft3 Rich
Diablo Chris