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Problem reading from 3 tables in mysql

开发者 https://www.devze.com 2022-12-23 13:25 出处:网络
What do I do, I need to fetch data from 3 tables in mysql, here is my current query. All of the tables contain the IDNO which has 03A45 number. But this query isnt returning any results:

What do I do, I need to fetch data from 3 tables in mysql, here is my current query. All of the tables contain the IDNO which has 03A45 number. But this query isnt returning any results:

SELECT * 
  FROM father, mother, parents 
 WHERE father.IDNO=mother.IDNO=parents.ID开发者_运维知识库NO 
   AND mother.IDNO='03A45' 
   AND father.IDNO='03A45' 
   AND parents.IDNO='03A45'

What would be the correct query for this?

All of the tables have the IDNO as primary key.


Something like this should work:

select *
from
father 
inner join mother on father.IDNO = mother.IDNO
inner join parents on mother.IDNO = parents.IDNO
where
father.IDNO = '03a45'


Use:

SELECT p.*,
       f.*,
       m.* 
  FROM PARENTS p
  JOIN FATHER f ON f.idno = p.idno
  JOIN MOTHER m ON m.idno = p.idno
 WHERE p.idno = '03A45'


The following code you've entered don't work because you entered a wrong sql command:

Dim sqlcom As MySqlCommand = New MySqlCommand("Select * from mother, father, parents INNER JOIN mother on father.IDNO = mother.IDNO, INNER JOIN parents on mother.IDNO = parents.IDNO WHERE father.IDNO='" & TextBox14.Text & "'", sqlcon)

The good query is the query give by Kristian

The principle on Inner Join is to join 2 tables:

The syntax is :

Select a.myFields, b.myFields
FROM myFirstTable as a INNER JOIN mySecondTable ON a.PrimaryKey = b.ForeignKey
INNER JOIN myThirdTable as c ON a.PrimaryKey = c.ForeighKey 'For 3Tables

It's just an example and you can use many others table.

Keep an eye on Sql courses. It's very powerful when you understand how it's working

Julien

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