Re: [PHP-DB] IF Clause in Left Join

> I really need some help.  I'm trying to use an IF statement in a multi-table
> left join.  I'm joining four tables (customers, contents, courses &
> locations).

IF can only be used in the select part or the where part, it can't be
used in the join part of a query.

> In the contents table I have two fields, product_id and value_id that relate
> to different values in different tables depending upon the value in the
> product_type field.  If product_type='course' then the product_id and
> value_id relate to the courses and locations table, but if
> product_type='other' then the product_id and value_id relate to the product
> and prices table.
>
> I have two options:
>
>  1.  Match only the courses and locations where product_type='course' and
> NULL values if relating to the product and prices table.
>  2.  Or change the query (and fields) if the product_type='other' to use the
> product and prices table.

You can union the results.

select ... where product_type='course'
union
select ... where product_type='other'

> I'm using Mysql 4.3.

Didn't know there was such a version ;)

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