Mysql multiple left join

Question

We have one table say table A we left join with table B. This works fine. The issue here is that based on the left join of table A and B we would like to have another left join but between table B and table C because those fields are available only in this 2 table so what is best solution to build this query?

its the same as joining tables a and b, but the on clause is going to reference tables b and c — Dale
– Dale, Commented Jul 31, 2012 at 5:35

Marc B · Accepted Answer · 2012-07-31 05:36:05Z

18

You can chain joins quite easily:

SELECT ...
FROM a
LEFT JOIN b on a.somefield=b.somefield
LEFT JOIN c on b.otherfield=c.otherfield

answered Jul 31, 2012 at 5:36

Marc B

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7 Comments

user837306 Over a year ago

yes your solution works any tips for optimisation for this query or this the best solution ready?

yunzen Over a year ago

This is the best solution. You can help the MySQL server to optimize by adding keys to the table

user837306 Over a year ago

@yunzen you mean index the fields rite nothing more then rite?

yunzen Over a year ago

Rite? What do you mean by that?

Marc B Over a year ago

right? simple rule of thumb for indexes: any field used in a join, in a where clause, or an order-by should be indexed. basically anywhere the field is used in a decision-making capacity.

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