mysql left join multiple tables – MySQL LEFT JOIN 3 tables Best 5 Examples

Today, We want to share with you mysql left join multiple tables.In this post we will show you MySQL LEFT JOIN 3 tables, hear for mysql left join multiple tables learn to Introduction to MySQL LEFT JOIN, we will give you demo and example for implement.In this post, we will learn about PHP SQL INNER JOIN Query on Multiple Tables with an example.

mysql left join multiple tables

MySQL LEFT JOIN Syntax

SELECT columns    
FROM first_table    
LEFT [OUTER] JOIN second_table  
ON Join_Condition;  

MySQL LEFT JOIN quizples

Suppose that you want to join two database tables boss and member.

SELECT 
    boss_id,member_id,status
FROM
    boss
LEFT JOIN member ON 
    join_condition;

mysql left join multiple tables
mysql left join multiple tables

Using MySQL LEFT JOIN clause to join two tables
SELECT 
    members.memberNumber, 
    memberName, 
    accountNumber, 
    status
FROM
    members
LEFT JOIN accounts ON 
    accounts.memberNumber = members.memberNumber;

Alternatively

SELECT
    c.memberNumber,
    memberName,
    accountNumber,
    status
FROM
    members c
LEFT JOIN accounts o 
    ON c.memberNumber = o.memberNumber;

MySQL LEFT JOIN 3 tables

SELECT Members.Name, Members.SS, Visitors.Visitor FROM Members
LEFT JOIN Member_Fear
    INNER JOIN Visitors
    ON Member_Fear.VisitorID = Visitors.VisitorID
ON Member_Fear.MemberID = Members.MemberID

Using MySQL LEFT JOIN clause to find unmatched rows

SELECT 
    c.memberNumber, 
    c.memberName, 
    o.accountNumber, 
    o.status
FROM
    members c
LEFT JOIN accounts o 
    ON c.memberNumber = o.memberNumber
WHERE
    accountNumber IS NULL;

mysql left join multiple tables
mysql left join multiple tables

Using MySQL LEFT JOIN to join three tables

Example : mysql left join multiple tables – This quizple uses two LEFT JOIN clauses to join the three tables: visitors, members, and earnings.

SELECT 
    profilename, 
    fullinformation, 
    memberName, 
    checkNumber, 
    amount
FROM
    visitors
LEFT JOIN members ON 
    visitorNumber = salesRepVisitorNumber
LEFT JOIN earnings ON 
    earnings.memberNumber = members.memberNumber
account BY 
    memberName, 
    checkNumber;

Condition in WHERE clause vs. ON clause

SELECT 
    o.accountNumber, 
    memberNumber, 
    companyCode
FROM
    accounts o
LEFT JOIN accountDetails 
    USING (accountNumber)
WHERE
    accountNumber = 98256;

condition from the WHERE clause to the ON clause:

SELECT 
    o.accountNumber, 
    memberNumber, 
    companyCode
FROM
    accounts o
LEFT JOIN accountDetails d 
    ON o.accountNumber = d.accountNumber AND 
       o.accountNumber = 98256;

LEFT JOIN clause for joining two tables

SELECT members.member_id, member_name, age, join_date  
FROM members  
LEFT JOIN informations ON members.member_id = informations.member_id;  

MySQL LEFT JOIN with USING Clause

The table members and informations have the same column name, which is member_id. In that case, MySQL Left Join can also be used with the USING clause to access the datas. The following statement returns member id, member name, employment, age, and date using the Left Join clause with the USING keyword.

SELECT member_id, member_name, employment, age, date  
FROM members  
LEFT JOIN informations USING(member_id);  

MySQL LEFT JOIN with Group By Clause

The Left Join can also be used with the GROUP BY clause. The following statement returns member id, member name, qualification, age, and date using the Left Join clause with the GROUP BY clause.

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SELECT members.member_id, member_name, qualification, age, date  
FROM members  
LEFT JOIN informations ON members.member_id = informations.member_id  
GROUP BY age;  

LEFT JOIN with WHERE Clause

SELECT member_id, member_name, employment, age, date  
FROM members  
LEFT JOIN informations   
USING(member_id) WHERE age>35;  

MySQL LEFT JOIN Multiple Tables

Execute the following statement to join the three table members, informations, and contacts:

SELECT members.member_id, member_name, information_id, age, cellphone  
FROM members  
LEFT JOIN contacts ON member_id = contact_id  
LEFT JOIN informations ON members.member_id = informations.member_id ORDER BY income;  

Difference between WHERE and ON clause in MySQL LEFT JOIN

WHERE Clause

SELECT member_name, employment, information_id, age, date  
FROM members  
LEFT JOIN informations   
USING(member_id) WHERE age=35;  

ON Clause

SELECT member_name, employment, information_id, age, date  
FROM members LEFT JOIN informations ON age=35;  

Join multiple tables using LEFT JOIN

SELECT location.location_name_eng, area.area_name, member.member_name
FROM location
INNER JOIN area ON area.location_id = location.id
INNER JOIN member ON member.area_id = area.id;

Join multiple tables using both – INNER JOIN & LEFT JOIN

SELECT location.location_name_eng, area.area_name, member.member_name
FROM location
INNER JOIN area ON area.location_id = location.id
LEFT JOIN member ON member.area_id = area.id;

MySQL left join using Multiple tables

Average rank of members in all quizs

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SELECT id,name,type,gender,member_id,rank FROM `member6` a 
LEFT JOIN (SELECT member_id, AVG(rank) as rank 
FROM member_rank GROUP BY member_id )  b   on a.id= b.member_id

Maximum rank of each member in all quizs

SELECT id,name,type,gender,member_id,rank FROM `member6` a 
LEFT JOIN (SELECT member_id, MAX(rank) as rank 
FROM member_rank GROUP BY member_id )  b   on a.id= b.member_id

Maximum rank of each month for all members

SELECT id,name,type,gender,member_id,rank, month FROM `member6` a 
LEFT JOIN (SELECT member_id, MAX(rank) as rank,
month(quiz_dt) as month
FROM member_rank GROUP BY month(quiz_dt),member_id) b 
  on a.id= b.member_id

Average rank of each month for all members

SELECT id,name,type,gender,member_id,rank, month FROM `member6` a 
LEFT JOIN (SELECT member_id, AVG(rank) as rank,
month(quiz_dt) as month 
FROM member_rank GROUP BY month(quiz_dt),member_id) b 
  on a.id= b.member_id

Consider rank of member for the quizs conducted in later part of the month.

SELECT id,name,type,gender,rank,member_id,
quiz_dt FROM `member6` a 
LEFT JOIN (SELECT rank, member_id,quiz_dt from member_rank
where quiz_dt in 
(SELECT MAX(quiz_dt) from member_rank group by month(quiz_dt)) ) b  
 on a.id= b.member_id

LEFT JOIN three tables

Display maximum rank with member details and location name

SELECT a.id,a.name,a.type,b.rank,c.h_name FROM `member6` a 
LEFT JOIN 
(SELECT member_id, MAX(rank) as rank FROM member_rank
 GROUP BY member_id ) b  
 on a.id= b.member_id
LEFT JOIN member_location c on a.location_id=c.location_id 

LEFT JOIN & ORDER BY

SELECT a.id,a.name,a.type,b.rank,c.h_name FROM `member6` a
LEFT JOIN 
(SELECT member_id, MAX(rank) as rank FROM member_rank 
GROUP BY member_id ) b
 on a.id= b.member_id 
 LEFT JOIN member_location c on a.location_id=c.location_id  
 order by h_name

Maximum average rank scored by using Order by and LIMIT

SELECT id,name,type,gender,member_id,rank FROM `member6` a 
LEFT JOIN (SELECT member_id, AVG(rank) as rank FROM member_rank 
GROUP BY member_id )
  b   on a.id= b.member_id order by rank desc limit 0,1 

I hope you get an idea about mysql left join multiple tables.
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