I have two tables in MySQL
and
I want to show Categories in place of Cid in first table. I'm using following query:
SELECT id,categorymass.Cid,video.Name
from video inner join categorymass on video.Cid = categorymass.Cid
What is problem in my inner join
Well You are not selecting category...
SELECT id,categorymass.Cid, categorymass.Category,video.Name
from video inner join categorymass on video.Cid = categorymass.Cid
Try this it will work :
SELECT t2.`Cid`, t2.`Category`,t1.`Name`
from video t1 JOIN categorymass t2 on t1.`Cid` = t2.`Cid`
Related
When I use a left join on different databases, it works but not when I use inner join. Why ?
SELECT tkblue_tklabel_dev_data.EmailContent.*, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
FULL JOIN tkblue_tklabel_dev_archdata.EmailTracking ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking
Unknown table 'tkblue_tklabel_dev_data.EmailContent'
But when using
SELECT tkblue_tklabel_dev_data.EmailContent.*, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
LEFT JOIN tkblue_tklabel_dev_archdata.EmailTracking ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking =
tkblue_tklabel_dev_data.EmailContent.idEmailTracking
I have not this error message, but I can only have the results of the left table. Or, I wish all the results like an full join.
Full join don't exists in mysql but you can produce the same result using both left join and right join in UNION
SELECT tkblue_tklabel_dev_data.EmailContent.*
, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
LEFT JOIN tkblue_tklabel_dev_archdata.EmailTracking
ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking
UNION
SELECT tkblue_tklabel_dev_data.EmailContent.*
, tkblue_tklabel_dev_archdata.EmailTracking.*
FROM tkblue_tklabel_dev_data.EmailContent
RIGHT JOIN tkblue_tklabel_dev_archdata.EmailTracking
ON tkblue_tklabel_dev_archdata.EmailTracking.idEmailTracking = tkblue_tklabel_dev_data.EmailContent.idEmailTracking
this is how i manage to join the table using inner join
SELECT lab5enrollment.matricno, lab5student.stuname,
lab5enrollment.courseid,
lab5course.cname
FROM ((lab5enrollment
INNER JOIN lab5student ON lab5enrollment.matricno = lab5student.matricno)
INNER JOIN lab5course ON lab5enrollment.courseid = lab5course.courseid)
WHERE lab5enrollment.courseid = 'CSF3402';
this is how i used the using keyword to join the table but i dont know how to join the three table...
SELECT matricno, stuname, courseid, cname
FROM lab5enrollment
JOIN lab5student
USING (matricno)
WHERE courseid = 'CSF3402';
i want to observe the differrence between using the inner join and using...
You should probably lean towards using joins with explicit ON clauses for a number of reasons. If you wanted to use USING here, then the following should work:
SELECT
t1.matricno,
t2.stuname,
t1.courseid,
t3.cname
FROM lab5enrollment t1
INNER JOIN lab5student t2
USING (matricno)
INNER JOIN lab5course t3
USING (courseid)
WHERE
t1.courseid = 'CSF3402';
This assumes that lab5enrollment and lab5student both have a column with the same name matricno, and that lab5student and lab5course both have a column called courseid.
I Have problem with joining 2 table
this is mysql query
select *
from tbl_perspective a
inner join tbl_objective b on b.idperspective=a.idperspective
The result is:
Query Result
I Want to display first row of perspectivename and blank or null
Final Result:
enter image description here
Hi Anwr Rawk simply you can use LEFT JOIN
select * from tbl_perspective as a
left join
tbl_objective as b
on b.idperspective=a.idperspective
Join to a subquery which identifies the first row for each idperspective group:
SELECT t1.*
FROM tbl_perspective t1
INNER JOIN
(
SELECT idperspective, MIN(idobjective) AS min_idobjective
FROM tbl_perspective
GROUP BY idperspective
) t2
ON t1.idperspective = t2.idperspective AND
t1.idobjective = t2.min_idobjective;
You need to use LEFT JOIN to include all results, like this : https://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins
I have two queries that result two result sets i need to compare both the result sets and need to display the differences between them.Hope i will get good support.Thank you.These are my queries
Query:1
SELECT distinct c.sid_ident,c.fix_ident from corept.std_sid_leg as c INNER JOIN (SELECT sid_ident, transition_ident, max(sequence_num) seq, route_type FROM corept.std_sid_leg WHERE data_supplier='J' AND airport_ident='KBOS' GROUP BY sid_ident,transition_ident) b ON c.sequence_num=b.seq and c.sid_ident = b.sid_ident and c.transition_ident =b.transition_ident WHERE c.data_supplier='J' and c.airport_ident='KBOS';
Query:2
SELECT name,trans FROM skyplan_deploy.deploy_sids ON d.name=c.sid_ident WHERE apt = 'KBOS' AND name != trans;
Comparison is to be done on fields sid_ident in corept.std_sid_leg and name in skplan_deplay.deploy_sids. As Mysql does not support full outer join,I thought of using left join and right join and combine both the results.But i stuck up with this.Please help.I am getting syntax error while using left and right join.Thank you.
The following query should simulate a FULL OUTER JOIN in MySQL.
SELECT *
FROM A
LEFT OUTER JOIN B
ON A.NAME = B.NAME
WHERE B.ID IS NULL
UNION ALL
SELECT *
FROM B
LEFT OUTER JOIN A
ON B.NAME = A.NAME
WHERE A.ID IS NULL;
Compare the results of the with an actual FULL OUTER JOIN in SQL Server and you'll see it works.
I want to replace the subquery with a join, if possible.
SELECT `fftenant_farmer`.`person_ptr_id`, `fftenant_surveyanswer`.`text_value`
FROM `fftenant_farmer`
INNER JOIN `fftenant_person`
ON (`fftenant_farmer`.`person_ptr_id` = `fftenant_person`.`id`)
LEFT OUTER JOIN `fftenant_surveyanswer`
ON fftenant_surveyanswer.surveyquestion_id = 1
AND fftenant_surveyanswer.`surveyresult_id` IN (SELECT y.`surveyresult_id` FROM `fftenant_farmer_surveyresults` y WHERE y.farmer_id = `fftenant_farmer`.`person_ptr_id`)
I tried:
SELECT `fftenant_farmer`.`person_ptr_id`, `fftenant_surveyanswer`.`text_value`#, T5.`text_value`
FROM `fftenant_farmer`
INNER JOIN `fftenant_person`
ON (`fftenant_farmer`.`person_ptr_id` = `fftenant_person`.`id`)
LEFT OUTER JOIN `fftenant_farmer_surveyresults`
ON (`fftenant_farmer`.`person_ptr_id` = `fftenant_farmer_surveyresults`.`farmer_id`)
LEFT OUTER JOIN `fftenant_surveyanswer`
ON (`fftenant_farmer_surveyresults`.`surveyresult_id` = `fftenant_surveyanswer`.`surveyresult_id`)
AND fftenant_surveyanswer.surveyquestion_id = 1
But that gave me one record per farmer per survey result for that farmer. I only want one record per farmer as returned by the first query.
A join may be faster on most RDBMs, but the real reason I asked this question is I just can't seem to formulate a join to replace the subquery and I want to know if it's even possible.
You could use DISTINCT or GROUP BY, as mvds and Brilliand suggest, but I think it's closer to the query's design intent if you change the last join to an inner-join, but elevating its precedence:
SELECT farmer.person_ptr_id, surveyanswer.text_value
FROM fftenant_farmer AS farmer
INNER
JOIN fftenant_person AS person
ON person.id = farmer.person_ptr_id
LEFT
OUTER
JOIN
( fftenant_farmer_surveyresults AS farmer_surveyresults
INNER
JOIN fftenant_surveyanswer AS surveyanswer
ON surveyanswer.surveyresult_id = farmer_surveyresults.surveyresult_id
AND surveyanswer.surveyquestion_id = 1
)
ON farmer_surveyresults.farmer_id = farmer.person_ptr_id
Broadly speaking, this will end up giving the same results as the DISTINCT or GROUP BY approach, but in a more principled, less ad hoc way, IMHO.
Use SELECT DISTINCT or GROUP BY to remove the duplicate entries.
Changing your attempt as little as possible:
SELECT DISTINCT `fftenant_farmer`.`person_ptr_id`, `fftenant_surveyanswer`.`text_value`#, T5.`text_value`
FROM `fftenant_farmer`
INNER JOIN `fftenant_person`
ON (`fftenant_farmer`.`person_ptr_id` = `fftenant_person`.`id`)
LEFT OUTER JOIN `fftenant_farmer_surveyresults`
ON (`fftenant_farmer`.`person_ptr_id` = `fftenant_farmer_surveyresults`.`farmer_id`)
LEFT OUTER JOIN `fftenant_surveyanswer`
ON (`fftenant_farmer_surveyresults`.`surveyresult_id` = `fftenant_surveyanswer`.`surveyresult_id`)
AND fftenant_surveyanswer.surveyquestion_id = 1
the real reason I asked this question is I just can't seem to formulate a join to replace the subquery and I want to know if it's even possible
Then consider a much simpler example to begin with e.g.
SELECT *
FROM T1
WHERE id IN (SELECT id FROM T2);
This is known as a semi join and if desired may be re-written using (among other possibilities) a JOIN with a SELECT clause to a) project only from the 'outer' table, and b) return only DISTINCT rows:
SELECT DISTINCT T1.*
FROM T1
JOIN T2 USING (id);