MySql Query: Left Join

Question

I am new Sql Queries.I wanted to make a table from difference of two tables.
Here's my query:

SELECT * FROM `question` WHERE `relatedFields` = 'Math' LEFT JOIN  `answer` ON `question`.ques = `answer`.ques where `answer`.TeacherNumber=1111111111

Please help.

If you need the where clause that should be always after the join clause and where makes a left join to an inner join. You need to provide some sample data and expected result out of it. — Abhik Chakraborty
– Abhik Chakraborty, Commented Sep 14, 2015 at 11:54

Harpreet Singh · Accepted Answer · 2015-09-14 12:06:47Z

2

Move the first WHERE clause to the end, and move that other where condition to ON to get true LEFT JOIN:

SELECT *
FROM `question`
  LEFT JOIN  `answer` ON `question`.ques = `answer`.ques
     and `answer`.TeacherNumber=1111111111
where `question`.relatedFields = 'Math'

Alternative syntax:

SELECT *
FROM
    (select * from `question` WHERE `relatedFields` = 'Math') as q
LEFT JOIN
    (select * from `answer` where TeacherNumber = 1111111111) as a
  ON q.ques = a.ques

edited Sep 14, 2015 at 12:06

Harpreet Singh

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answered Sep 14, 2015 at 11:55

jarlh

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Comments

Community · Accepted Answer · 2017-05-23 12:22:07Z

1

This post will help you to understand better the joins. It help me too.

Explanation about Joins click here.

edited May 23, 2017 at 12:22

CommunityBot

11 silver badge

answered Sep 14, 2015 at 12:04

user3812703

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