This question already has answers here:
mysql query show multiple tables from one ID column
(3 answers)
Closed 4 months ago.
I have tables like below,
Match table
date
team1
team2
2/2/2019
t001
t002
3/2/2019
t007
t002
Team table
teamID
teamName
t001
ABCD
t002
EFGH
t003
IJKL
t007
MNOP
I want to display Match table with teamName of team1 and team2 instead of teamID. I know I can join it as,
SELECT m.date, t.teamName, t.team2
FROM Match m INNER JOIN Team t
ON t.team1 = t.teamID;
But it can join with only one column. I don't know how to join both columns. Is there anyway to do this.
SELECT m.date, t.teamName, t1.teamName
FROM Match m INNER JOIN Team t
ON m.team1 = t.teamID
FROM Match m1 INNER JOIN Team t1
ON m1.team2 = t1.teamID;
or
SELECT m.date, t.teamName, t1.teamName
FROM Match m
INNER JOIN Team t ON m.team1 = t.teamID
INNER JOIN Team t1 ON m.team2 = t1.teamID;
It's the same
I don't understand the table name, why is a d.team2 if there is no alias d,. And why are team1 and team2 both also from table d.
But if I veratanden your two tables correctly the bottom query works.
But for multible joins you can just use different alias.
Related
I have three tables named
**Student Table**
-------------
id name
-------------
1 ali
2 ahmed
3 john
4 king
**Course Table**
-------------
id name
-------------
1 physic
2 maths
3 computer
4 chemistry
**Bridge**
-------------
sid cid
-------------
1 1
1 2
1 3
1 4
2 1
2 2
3 3
3 4
4 1
4 2
Now to show the student name with the course name which he had studied like,
**Result**
---------------------------
Student Course
---------------------------
ahmed physic
ahmed maths
ahmed computer
ahmed chemistry
ali physic
ali maths
john computer
john chemistry
king physic
king maths
I build following query
select s.name as Student, c.name as Course from student s, course c join bridge b on c.id = b.cid order by s.name
But it does not return the required result...
And what would be for normalized form, if I want to find who is manager over other:
**employee**
-------------------
id name
-------------------
1 ali
2 king
3 mak
4 sam
5 jon
**manage**
--------------
mid eid
--------------
1 2
1 3
3 4
4 5
And wants to get this result:
**result**
--------------------
Manager Staff
--------------------
ali king
ali mak
mak sam
sam jon
Use ANSI syntax and it will be a lot more clear how you are joining the tables:
SELECT s.name as Student, c.name as Course
FROM student s
INNER JOIN bridge b ON s.id = b.sid
INNER JOIN course c ON b.cid = c.id
ORDER BY s.name
Simply use:
select s.name "Student", c.name "Course"
from student s, bridge b, course c
where b.sid = s.sid and b.cid = c.cid
For normalize form
select e1.name as 'Manager', e2.name as 'Staff'
from employee e1
left join manage m on m.mid = e1.id
left join employee e2 on m.eid = e2.id
SELECT *
FROM user u
JOIN user_clockits uc ON u.user_id=uc.user_id
JOIN clockits cl ON cl.clockits_id=uc.clockits_id
WHERE user_id = 158
Don't join like that. It's a really really bad practice!!! It will slow down the performance in fetching with massive data. For example, if there were 100 rows in each tables, database server have to fetch 100x100x100 = 1000000 times. It had to fetch for 1 million times. To overcome that problem, join the first two table that can fetch result in minimum possible matching(It's up to your database schema). Use that result in Subquery and then join it with the third table and fetch it. For the very first join --> 100x100= 10000 times and suppose we get 5 matching result. And then we join the third table with the result --> 5x100 = 500. Total fetch = 10000+500 = 10500 times only. And thus, the performance went up!!!
join query with three tables and we want two values from the same column we set the alias name for every table in the joins. Same table name also declare as a different names.
const sql = `select p.ID,p.purchaseamount,urs.name as
buyername,pd.productname,
pd.amount,urs1.name as sellername
from purchases p
left join products pd on p.productid=pd.ID
left join users urs on p.userid=urs.ID
left join users urs1 on pd.userid=urs1.ID`
SELECT
employees.id,
CONCAT(employees.f_name," ",employees.l_name) AS 'Full Name', genders.gender_name AS 'Sex',
depts.dept_name AS 'Team Name',
pay_grades.pay_grade_name AS 'Band',
designations.designation_name AS 'Role'
FROM employees
LEFT JOIN genders ON employees.gender_id = genders.id
LEFT JOIN depts ON employees.dept_id = depts.id
LEFT JOIN pay_grades ON employees.pay_grade_id = pay_grades.id
LEFT JOIN designations ON employees.designation_id = designations.id
ORDER BY employees.id;
You can JOIN multiple TABLES like this example above.
Just adding a point to previous answers that in MySQL we can either use
table_factor syntax
OR
joined_table syntax
mysql documentation
Table_factor example
SELECT prd.name, b.name
FROM products prd, buyers b
Joined Table example
SELECT prd.name, b.name
FROM products prd
left join buyers b on b.bid = prd.bid;
FYI: Please ignore the fact the the left join on the joined table example doesnot make much sense (in reality we would use some sort of join table to link buyer to the product table instead of saving buyerID in product table).
Query for three table join and limit set
SELECT * FROM (SELECT t1.follower_userid, t2.*, t3.login_thumb, t3.login_name,
t3.bio, t3.account_status, t3.gender
FROM videos t2
LEFT JOIN follower t1
ON t1.follower_userid = t2.user_id
LEFT JOIN videos_user t3
ON t1.follower_userid = t3.login_userid
WHERE t1.following_userid='$userid'
LIMIT $startpoint , $limit) AS ID
ORDER BY ID DESC
Query to join more than two tables:
SELECT ops.field_id, ops.option_id, ops.label
FROM engine4_user_fields_maps AS map
JOIN engine4_user_fields_meta AS meta ON map.`child_id` = meta.field_id
JOIN engine4_user_fields_options AS ops ON map.child_id = ops.field_id
WHERE map.option_id =39 AND meta.type LIKE 'outcomeresult' LIMIT 0 , 30
Use this:
SELECT s.name AS Student, c.name AS Course
FROM student s
LEFT JOIN (bridge b CROSS JOIN course c)
ON (s.id = b.sid AND b.cid = c.id);
I have three tables named
**Student Table**
-------------
id name
-------------
1 ali
2 ahmed
3 john
4 king
**Course Table**
-------------
id name
-------------
1 physic
2 maths
3 computer
4 chemistry
**Bridge**
-------------
sid cid
-------------
1 1
1 2
1 3
1 4
2 1
2 2
3 3
3 4
4 1
4 2
Now to show the student name with the course name which he had studied like,
**Result**
---------------------------
Student Course
---------------------------
ahmed physic
ahmed maths
ahmed computer
ahmed chemistry
ali physic
ali maths
john computer
john chemistry
king physic
king maths
I build following query
select s.name as Student, c.name as Course from student s, course c join bridge b on c.id = b.cid order by s.name
But it does not return the required result...
And what would be for normalized form, if I want to find who is manager over other:
**employee**
-------------------
id name
-------------------
1 ali
2 king
3 mak
4 sam
5 jon
**manage**
--------------
mid eid
--------------
1 2
1 3
3 4
4 5
And wants to get this result:
**result**
--------------------
Manager Staff
--------------------
ali king
ali mak
mak sam
sam jon
Use ANSI syntax and it will be a lot more clear how you are joining the tables:
SELECT s.name as Student, c.name as Course
FROM student s
INNER JOIN bridge b ON s.id = b.sid
INNER JOIN course c ON b.cid = c.id
ORDER BY s.name
Simply use:
select s.name "Student", c.name "Course"
from student s, bridge b, course c
where b.sid = s.sid and b.cid = c.cid
For normalize form
select e1.name as 'Manager', e2.name as 'Staff'
from employee e1
left join manage m on m.mid = e1.id
left join employee e2 on m.eid = e2.id
SELECT *
FROM user u
JOIN user_clockits uc ON u.user_id=uc.user_id
JOIN clockits cl ON cl.clockits_id=uc.clockits_id
WHERE user_id = 158
Don't join like that. It's a really really bad practice!!! It will slow down the performance in fetching with massive data. For example, if there were 100 rows in each tables, database server have to fetch 100x100x100 = 1000000 times. It had to fetch for 1 million times. To overcome that problem, join the first two table that can fetch result in minimum possible matching(It's up to your database schema). Use that result in Subquery and then join it with the third table and fetch it. For the very first join --> 100x100= 10000 times and suppose we get 5 matching result. And then we join the third table with the result --> 5x100 = 500. Total fetch = 10000+500 = 10500 times only. And thus, the performance went up!!!
join query with three tables and we want two values from the same column we set the alias name for every table in the joins. Same table name also declare as a different names.
const sql = `select p.ID,p.purchaseamount,urs.name as
buyername,pd.productname,
pd.amount,urs1.name as sellername
from purchases p
left join products pd on p.productid=pd.ID
left join users urs on p.userid=urs.ID
left join users urs1 on pd.userid=urs1.ID`
SELECT
employees.id,
CONCAT(employees.f_name," ",employees.l_name) AS 'Full Name', genders.gender_name AS 'Sex',
depts.dept_name AS 'Team Name',
pay_grades.pay_grade_name AS 'Band',
designations.designation_name AS 'Role'
FROM employees
LEFT JOIN genders ON employees.gender_id = genders.id
LEFT JOIN depts ON employees.dept_id = depts.id
LEFT JOIN pay_grades ON employees.pay_grade_id = pay_grades.id
LEFT JOIN designations ON employees.designation_id = designations.id
ORDER BY employees.id;
You can JOIN multiple TABLES like this example above.
Just adding a point to previous answers that in MySQL we can either use
table_factor syntax
OR
joined_table syntax
mysql documentation
Table_factor example
SELECT prd.name, b.name
FROM products prd, buyers b
Joined Table example
SELECT prd.name, b.name
FROM products prd
left join buyers b on b.bid = prd.bid;
FYI: Please ignore the fact the the left join on the joined table example doesnot make much sense (in reality we would use some sort of join table to link buyer to the product table instead of saving buyerID in product table).
Query for three table join and limit set
SELECT * FROM (SELECT t1.follower_userid, t2.*, t3.login_thumb, t3.login_name,
t3.bio, t3.account_status, t3.gender
FROM videos t2
LEFT JOIN follower t1
ON t1.follower_userid = t2.user_id
LEFT JOIN videos_user t3
ON t1.follower_userid = t3.login_userid
WHERE t1.following_userid='$userid'
LIMIT $startpoint , $limit) AS ID
ORDER BY ID DESC
Query to join more than two tables:
SELECT ops.field_id, ops.option_id, ops.label
FROM engine4_user_fields_maps AS map
JOIN engine4_user_fields_meta AS meta ON map.`child_id` = meta.field_id
JOIN engine4_user_fields_options AS ops ON map.child_id = ops.field_id
WHERE map.option_id =39 AND meta.type LIKE 'outcomeresult' LIMIT 0 , 30
Use this:
SELECT s.name AS Student, c.name AS Course
FROM student s
LEFT JOIN (bridge b CROSS JOIN course c)
ON (s.id = b.sid AND b.cid = c.id);
Scenario is I have a list of fixtures as below.Fixtures are represented by team ids
Fixture Table
FixtureID HomeTeam AwayTeam
1 1 2
2 2 4
I need to then look to the Team table to grab the name of each team
Team Table
TeamID TeamName
1 Team1
2 Team2
I need to run a query which will grab the fixtures and change the TeamID's into the team name so it looks like
HomeTeam TeamName AwayTeam TeamName
1 Team1 2 Team2
2 Team2 4 Team4
At the moment I have
SELECT Fixtures.HomeTeam, Teams.TeamName, Fixtures.AwayTeam
FROM Fixtures INNER JOIN
Teams ON Fixtures.HomeTeam = Teams.TeamID
Which outputs:
HomeTeam TeamName AwayTeam
1 Donegal Celtic 2
2 Banbridge Town 1
3 Limavdy United 5
I am just having trouble getting the away team name to show.Any help would be appreciated.
You simply need two joins:
SELECT f.HomeTeam, th.TeamName, f.AwayTeam, ta.TeamName
FROM Fixtures f INNER JOIN
Teams th
ON f.HomeTeam = th.TeamID INNER JOIN
Teams ta
ON f.AwayTeam = ta.TeamId;
You need to join Team table twice, e.g.:
SELECT f.FixtureID, t1.TeamID, t1.name, t2.TeamID, t2.name
FROM fixtures f JOIN team t1 ON f.hometeam = t1.TeamID
JOIN team t2 on f.awayteam = t2.TeamID;
Here's the SQL Fiddle.
Join Teams table twice with Fixtures table.
SELECT Fixtures.HomeTeam, t1.TeamName, Fixtures.AwayTeam, t2.TeamName
FROM Fixtures INNER JOIN
Teams t1
ON Fixtures.HomeTeam = t1.TeamID
INNER JOIN
Teams t2
ON Fixtures.AwayTeam = t2.TeamId;
Working sample.
I have three tables: Players, PlayersArchive, Races. The Players and PlayersArchive tables are exactly the same structure.
In Players and PlayersArchive we have PlayerID and Name.
In Races we have in one row:
RaceID, Record1PlayerID, Record2PlayerID, Record3PlayerID, Record4PlayerID and Record5PlayerID
The task is to SELECT the whole Races table, but instead of the player ID fields it should return their names.
e.g.:
Races table:
RaceID: 1
Record1PlayerID: 2
Record2PlayerID: 1
Record3PlayerID: 0
Record4PlayerID: 0
Record5PlayerID: 0
Players table:
PlayerID: 1
Name: Jhon
PlayersArchive table:
PlayerID: 2
Name: Jack
result:
1 Jack Jhon NULL NULL NULL
You have two problems with your data structure. The first is that you should have a separate table for the players in each race, with one row per player/race combination. Putting them in separate columns on a single row is a bad idea.
The second problem is putting the names in two different tables. From your question, I cannot tell if both the players table and playersarchive table are necessary. So, I'll assume the archive is not necessary.
The solution is to join from the races table to the table with the players information:
select r.*,
p1.name as name1,
p2.name as name2,
p3.name as name3,
p4.name as name4,
p5.name as name5
from races r left outer join
players p1
on r.record1playerid = p1.playerid left outer join
players p2
on r.record1playerid = p2.playerid left outer join
players p3
on r.record1playerid = p3.playerid left outer join
players p4
on r.record1playerid = p4.playerid left outer join
players p5
on r.record1playerid = p5.playerid left outer join
If the data is really in both Players and PlayersArchive, then players might need to be:
(select distinct playerid, name from ((select p.* from players) union all (select pa.* from playersarchive)) t) p1 . . .
This combines the two tables together for looking up the name.
This will only demonstrate a posible solution to what you ask.
Select RaceId, p1.Name AS Name1 From Races AS r
Left Join (
Select * From Players
Union Select * From PlayersArchive
) AS p1 On r.Record1PlayerID = p1.PlayerID;
You should repeat this left join 4 more times whithin your query to get all 5 names.
Please note that with big data this might take a long time to execute.
I am planning to create a website similar to IMDB.com. To reduce execution time I am using the following structure. Is it okay for faster working?
Table - 1
Id Movie_name description
1 name one some description
2 name two some description
3 name three some description
Table 2
id actorname
1 name 1
2 name 2
3 name 3
4 name 4
Table 3
id movieid actorid
1 1 1
2 1 2
3 1 3
4 1 9
5 2 6
6 2 5
7 2 8
8 2 1
When I want to list actors in a movie program will retrieve actors ids from table 3 and find respective names from table 2 (using single query). When I want to list the movies of a actor it will retrieve movie ids from table 3 and find respective names from first table. Will it work properly? Any other ideas?
This will give all actors in a specified movie,
SELECT c.ID, c.actorName
FROM table1 a
INNER JOIN table3 b
ON a.ID = b.movieID
INNER JOIN table2 c
ON b.actorid = c.ID
WHERE a.ID = 1
This one will give all movies for a specified actor
SELECT a.*
FROM table1 a
INNER JOIN table3 b
ON a.ID = b.movieID
INNER JOIN table2 c
ON b.actorid = c.ID
WHERE c.ID = 1
SQLFiddle Demo (both queries)
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
UPDATE 1
This is called Relational Division
SELECT a.ID, a.Movie_Name
FROM table1 a
INNER JOIN table3 b
ON a.ID = b.movieID
INNER JOIN table2 c
ON b.actorid = c.ID
WHERE c.ID IN (1, 2, 3)
GROUP BY a.ID, a.Movie_Name
HAVING COUNT(DISTINCT c.ID) = 3
SQL of Relational Division
I suggest that you modify table3 by taking away the id field. Use the movieid and actorid together as your primary key. You might want to add other fields to this table such as name of character and order of appearance as suggested in the comment by Jermaine Xu.