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FooKelvin

Join Multiple table

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Hi Guys, i have a problem regarding on joining multiple tables, i was trying up for few days, but still can't get it done. This database is to join employee survey question regarding to one of the cafe. 

 

Below are my current non-working query.

SELECT question.*, question_options.*, answer.*,txtanswer.*
FROM question
    LEFT JOIN question_options
        ON question.question_id = question_options.question_id
    LEFT JOIN answer
        ON answer.option_id = question_options.qtn_option_id
	 JOIN txtanswer
		ON txtanswer.qtn_option_id= question_options.qtn_option_id
		WHERE answer.empid = 'EMP8969' 

This query show no result when i join to the txtanswer table.

Please download the attachment to view my table data. 

 

Thanks for your help.

Jointable.zip

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I'd make a couple of changes

 

  1. move the WHERE condition to the JOIN condition for the answer table
  2. use a LEFT join for the txtanswer table
SELECT question.*, question_options.*, answer.*,txtanswer.*
FROM question
    LEFT JOIN question_options
        ON question.question_id = question_options.question_id
    LEFT JOIN answer
        ON answer.option_id = question_options.qtn_option_id
           AND answer.empid = 'EMP8969' 
	 LEFT JOIN txtanswer
		ON txtanswer.qtn_option_id= question_options.qtn_option_id
		 

And don't use *s in the SELECT, specify the required fields.

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