Query :
SELECT *
FROM dbo.employer_job
LEFT JOIN dbo.employer_user
ON dbo.employer_job.employer_id = dbo.employer_user.employer_user_id
LEFT JOIN dbo.company_profile
ON dbo.company_profile.company_id = dbo.employer_user.company_id
Duplicate column results :
dbo.employer_job schema :
dbo.employer_user schema :
dbo.comnpany_profile schema :
How do I remove the duplicate company_id column? My Python app won't accept duplicated columns from the database. Most suggest to use left join but that's not solving the issue.
Don't use *, but list the columns you want from each table (preferably with an alias).
SELECT EJ.job_id, EJ.employer_id, ....
FROM dbo.employer_job EJ
...
It's verbose, but how else would the database engine know what you'd like to see?
You need to list the columns explicitly -- and qualify them:
SELECT ej.*, eu.employee_user_email,
cp.company_name, . . .
FROM dbo.employer_job ej LEFT JOIN
dbo.employer_user eu
ON ej.employer_id = eu.employer_user_id LEFT JOIN
dbo.company_profile cp
ON cp.company_id = eu.company_id;
I'm not sure if the LEFT JOIN is really needed. Note that this introduces table aliases, so the query is easier to write and to read.
Related
Below is a join based on where clause:
SELECT a.* FROM TEST_TABLE1 a,TEST_TABLE2 b,TEST_TABLE3 c
WHERE a.COL11 = b.COL11
AND b.COL12 = c.COL12
AND a.COL3 = c.COL13;
I have been learning SQL from online resources and trying to convert it with joins
Two issues:
The original query is confusing. The outer joins (with the (+) suffix) are made irrelevant by the last where condition. Because of that condition, the query should only return records where there is an actual matching c record. So the original query is the same as if there were no such (+) suffixes.
Your query joins TEST_TABLE3 twice, while the first query only joins it once, and there are two conditions that determine how it is joined there. You should not split those conditions over two separate joins.
BTW, it is surprising that the SQL Fiddle site does not show an error, as it makes no sense to use the same alias twice. See for example how MySQL returns the error with the same query on dbfiddle (on all available versions of MySQL):
Not unique table/alias: 'C'
So to get the same result using the standard join notation, all joins should be inner joins:
SELECT *
FROM TEST_TABLE1 A
INNER JOIN TEST_TABLE2 B
ON A.COL11 = B.COL11
INNER JOIN TEST_TABLE3 C
ON A.COL11 = B.COL11
AND B.COL12 = C.COL12;
#tricot correctly pointed out that it's strange to have 2 aliases with the same name and not getting an error. Also, to answer your question :
In the first query, we are firstly performing cross join between all the 3 tables by specifying all the table names. After that, we are filtering the rows using the condition specified in the WHERE clause on output that we got after performing cross join.
In second query, you need to join test_table3 only once. Since now you have all the required aliases A,B,C as in the first query so you can specify 2 conditions after the last join as below:
SELECT A.* FROM TEST_TABLE1 A
LEFT JOIN TEST_TABLE2 B
ON A.COL11 = B.COL11
left join TEST_TABLE3 C
on B.COL12 =C.COL12 AND A.COL3 = C.COL13;
I am trying to write a SQL Select statement to port some data from a Sybase environment to a MongoDB environment and I'm just trying to figure out the correct syntax to involve three different tables.
Basically what I need to do is do an INNER JOIN on two tables, and then do a matching check against a 3rd table. The three table names are "ar_notes", "customer_service_xref" and "service_notes_details"
This is what I tried:
SELECT * FROM ar_notes arn
LEFT JOIN customer_service_xref csx ON arn.customer_service_xref_id = csx.id_number
WHERE arn.visit_date = service_notes_details.date_of_visit
This doesn't work. I get a correlation error.
What should the syntax look like when involving three tables like this?
You said you need an INNER JOIN among three tables but your query does a LEFT JOIN between two and tries another join in the WHERE clause without refering that table in the FROM clause.
To just fix your query:
SELECT *
FROM service_notes_details snd, ar_notes arn
INNER JOIN customer_service_xref csx ON arn.customer_service_xref_id = csx.id_number
WHERE arn.visit_date = snd.date_of_visit
This is what you should use in current SQL syntax:
SELECT *
FROM ar_notes arn
INNER JOIN customer_service_xref csx ON arn.customer_service_xref_id = csx.id_number
INNER JOIN service_notes_details ON arn.visit_date = service_notes_details.date_of_visit
To be clear, this will only return lines in ar_notes that have corresponding values in customer_service_xref (joining by customer_service_xref_id) and in service_notes_details(joining by visit_date). Your original query, using LEFT JOIN would return lines from ar_notes even if there was no matching customer_service_xref_id.
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 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.
Ok.. So I'm trying to improve my SQL skills and have a question. Here is a screen shot of the schema.
Schema http://img509.imageshack.us/img509/97/screenhunter02nov121946.gif
(http://img509.imageshack.us/img509/97/screenhunter02nov121946.gif)
Alright so I'm selecting a bunch of Report Bundles and other rows from a table you can see. I've got these two tables joining together correctly and displaying what should be returned. Now I need to add another field onto my result rows that states what type of report this is. How can I join up to the ReportGroupType table through the ReportBundleGroup table without getting a shwack of results?
Here is the query I am using so far.
SELECT *
FROM ReportBundleCustomerVisibility INNER JOIN ReportBundle
ON ReportBundleCustomerVisibility.ReportBundleID = ReportBundle.ID
WHERE ReportBundleCustomerVisibility.ReferenceCustomerID = 2303
Thanks again SO
SELECT *
FROM ReportBundleCustomerVisibility AS v
JOIN ReportBundle AS b ON b.ID = v.ReportBundleID
JOIN ReportBundleGroup AS g ON b.ID = g.ReportBundleID
JOIN ReportGroupTYpe AS t ON t.ID = g.ReportGroupTypeID
WHERE v.ReferenceCustomerID = 2303
It sounds like you just need another inner join to get the information you need. You can think about the second join as joining the result of the join with the ReportGroupType table. I added parenthesis to try to join the two sets the second INNER JOIN is operating on.
SELECT * FROM ((ReportBundleCustomerVisibility
INNER JOIN ReportBundle ON ReportBundleCustomerVisibility.ReportBundleID = ReportBundle.ID)
INNER JOIN ReportGroupType ON ReportBundleGroup.ReportGroupTypeID = ReportGroupType.ID)
WHERE ReportBundleCustomerVisibility.ReferenceCustomerID = 2303
I also highly suggest against using "SELECT *" in production code or any query you plan on reusing as the table schema can change and possibly effect reports and UI. Explicitly specify the columns instead.