Results by querying two different datatables....

[Jim R]

I can't seem to wrap it around my head how to get a desired result from querying two tables.  I get two or multiple columns but not when it involves two tables.

 

It's a WordPress query.  I'm trying to:

 

SELECT name FROM wp_terms WHERE (this is where I stumble)...

 

where  taxonomy from wp_term_taxonomy = post_tag

AND

term_id from wp_term_taxonomy = term_id from wp_teams

 

[trq]

You'll want to do a few tutorials on JOINs.

[Jim R]

As I said, I'm not really able to wrap my head around it. 

[trq]

So you want us to write you another one? What don;t you understand? What code have you tried? What errors are you getting?

[fenway]

Post the two table structures, and we'll give you a hand.

[Jim R]

That is the table structure as best as I can tell. 

 

The two tables are wp_term and wp_term_taxonomy. 

I'm trying to extract results from "name" in wp_term, where "taxonomy" in wp_term_taxonomy is post_tag, matching them by "term_id", which is in both tables.

[fenway]

select wp.term.name

from wp_term

inner join wp_term_taxonomy using ( term_id )

[Jim R]

That just prints all the term.  I'm trying to get the ones that just have post_tag as their taxonomy.  I tried this, but I get a syntax error.

 

SELECT wp_terms.name
FROM wp_terms
INNER JOIN wp_term_taxonomy USING (term_id)
WHERE wp_term_taxonomy.taxonomy IS (post_tag)

[Jim R]

Got it.  Thanks.

 

SELECT wp_terms.name

FROM wp_terms

INNER JOIN wp_term_taxonomy USING (term_id)

WHERE wp_term_taxonomy.taxonomy = 'post_tag'

[Jim R]

Continuing with this project, I need to alter a column in one table based on what it matches in the other. 

 

tables are:

wp_term_taxonomy_test

wp_term_taxonomy

 

UPDATE wp_term_taxonomy_test
SET wp_term_taxonomy_test.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
WHERE wp_term_taxonomy.term_id = wp_term_taxonomy_test.term_id

 

The error I'm getting is that  wp_term_taxonomy.term_id    doesn't exist.  However, it does exist.

 

Error Code : 1054

Unknown column 'wp_term_taxonomy.term_id' in 'where clause'

 

[fenway]

You'll need a similar JOIN -- you haven't reference the second table.

[Jim R]

Ooops...sorry.  I had figured that out but didn't follow up.  Thank you for your help.