Tax queries and meta queries in Wordpress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a tax query in WordPress?

A tax query lets you filter posts based on taxonomy terms like categories or tags. It helps you get posts that belong to specific groups.

beginner

What is a meta query in WordPress?

A meta query filters posts by custom fields (post meta). It lets you find posts with specific meta key and value pairs.

intermediate

How do you combine tax queries and meta queries in WP_Query?

You add both 'tax_query' and 'meta_query' arrays inside the WP_Query arguments. WordPress will filter posts that match both conditions.

intermediate

What does the 'relation' key do in tax_query or meta_query arrays?

The 'relation' key sets how multiple conditions are combined: 'AND' means all must match, 'OR' means any can match.

intermediate

Give an example of a meta_query to find posts where 'price' is greater than 20.

Example: 'meta_query' => [ ['key' => 'price', 'value' => 20, 'compare' => '>', 'type' => 'NUMERIC'] ]

Which argument do you use to filter posts by taxonomy terms in WP_Query?

A category_name

B meta_query

C tax_query

D post_type

The 'tax_query' argument filters posts by taxonomy terms like categories or tags.

What does the 'meta_query' filter in WordPress?

A Post categories

B Post dates

C Post authors

D Custom fields (post meta)

'meta_query' filters posts based on custom fields (post meta) values.

How do you combine multiple conditions inside a tax_query?

A Using 'combine' key with 'ALL'

B Using 'relation' key with 'AND' or 'OR'

C Using 'join' key with 'AND'

D Using 'filter' key with 'OR'

The 'relation' key defines how multiple tax_query conditions are combined, either 'AND' or 'OR'.

Which compare operator would you use in meta_query to find posts with a meta value less than 100?

A <

B >

C =

D LIKE

Use '<' to find meta values less than a specified number.

If you want posts that match either one taxonomy term or another, which 'relation' value should you use?

A OR

B NOT

C AND

D XOR

'OR' means posts matching any of the taxonomy terms will be included.

Explain how to use tax_query and meta_query together in a WP_Query to filter posts.

Think about filtering posts by categories and custom fields at the same time.

Describe the purpose of the 'relation' key in tax_query or meta_query arrays.

It’s like deciding if you want all or any conditions to be true.

Practice

1. Which of the following best describes a tax_query in WordPress?

easy

A. It filters posts based on custom field values.

B. It sorts posts by date or title.

C. It filters posts based on categories, tags, or custom taxonomies.

D. It updates post metadata values.

Solution

1. Step 1: Understand tax_query purpose

   A tax_query is used to filter posts by taxonomy terms like categories or tags.

2. Step 2: Compare with meta_query

   A meta_query filters by custom fields, not taxonomies.

3. Final Answer:

   It filters posts based on categories, tags, or custom taxonomies. -> Option C

4. Quick Check:

   tax_query = taxonomy filter [OK]

Hint: Tax queries filter by taxonomy terms like categories [OK]

Common Mistakes:

• Confusing tax_query with meta_query
• Thinking tax_query sorts posts
• Assuming tax_query updates data

2. Which of the following is the correct syntax to create a meta query filtering posts where the meta key 'color' equals 'blue'?

easy

A. tax_query => [ ['taxonomy' => 'color', 'field' => 'slug', 'terms' => 'blue'] ]

B. meta_query => [ ['key' => 'color', 'value' => 'blue', 'compare' => '='] ]

C. meta_query => [ ['key' => 'color', 'value' => 'blue', 'compare' => 'LIKE'] ]

D. meta_query => [ ['key' => 'color', 'value' => ['blue'], 'compare' => 'IN'] ]

Solution

1. Step 1: Identify meta_query structure

   A meta query uses 'key', 'value', and 'compare' keys to filter custom fields.

2. Step 2: Match exact equality

   To check exact match, 'compare' should be '=' and 'value' a string, not array.

3. Final Answer:

   meta_query => [ ['key' => 'color', 'value' => 'blue', 'compare' => '='] ] -> Option B

4. Quick Check:

   Exact match uses compare '=' [OK]

Hint: Use compare '=' for exact meta key-value match [OK]

Common Mistakes:

• Using tax_query instead of meta_query
• Using 'LIKE' when exact match needed
• Passing value as array when not needed

3. What will the following query return?

query_posts([
  'tax_query' => [[
    'taxonomy' => 'category',
    'field' => 'slug',
    'terms' => ['news', 'updates'],
    'operator' => 'AND'
  ]],
  'meta_query' => [[
    'key' => 'featured',
    'value' => '1',
    'compare' => '='
  ]]
]);

medium

A. Syntax error due to incorrect tax_query format.

B. Posts in either 'news' OR 'updates' categories with meta 'featured' = '1'.

C. Posts with meta 'featured' = '1' ignoring categories.

D. Posts in both 'news' AND 'updates' categories with meta 'featured' = '1'.

Solution

1. Step 1: Analyze tax_query operator

   Operator 'AND' means posts must be in both 'news' and 'updates' categories simultaneously.

2. Step 2: Analyze meta_query condition

   Meta query filters posts where 'featured' meta key equals '1'.

3. Final Answer:

   Posts in both 'news' AND 'updates' categories with meta 'featured' = '1'. -> Option D

4. Quick Check:

   tax_query 'AND' + meta_query '=' = Posts in both 'news' AND 'updates' categories with meta 'featured' = '1'. [OK]

Hint: Operator 'AND' means all terms must match in tax_query [OK]

Common Mistakes:

• Confusing 'AND' with 'OR' operator
• Ignoring meta_query filter
• Assuming syntax error incorrectly

4. Identify the error in this tax query:

$args = [
  'tax_query' => [
    'taxonomy' => 'genre',
    'field' => 'slug',
    'terms' => 'fiction'
  ]
];
$query = new WP_Query($args);

medium

A. tax_query must be an array of arrays, but here it's a single array.

B. The 'terms' value must be an array, not a string.

C. The 'field' key is invalid in tax_query.

D. WP_Query does not accept tax_query parameter.

Solution

1. Step 1: Check tax_query structure

   tax_query expects an array of arrays, each inner array defines one taxonomy filter.

2. Step 2: Identify the provided structure

   Here tax_query is a single associative array, missing the outer array wrapping.

3. Final Answer:

   tax_query must be an array of arrays, but here it's a single array. -> Option A

4. Quick Check:

   tax_query = array of arrays [OK]

Hint: tax_query always needs an outer array wrapping inner arrays [OK]

Common Mistakes:

• Passing single array instead of array of arrays
• Thinking 'terms' must always be array
• Ignoring tax_query structure rules

5. You want to query posts that are in the 'events' category AND have a custom field 'priority' set to 'high'. Which is the correct way to combine tax_query and meta_query to achieve this?

medium

A. Use 'relation' => 'AND' to combine tax_query and meta_query for AND behavior.

B. Nest tax_query and meta_query inside a 'relation' => 'OR' array within 'meta_query'.

C. Combine tax_query and meta_query inside a single array without 'relation'.

D. Use 'relation' => 'OR' at the top level combining tax_query and meta_query arrays.

Solution

1. Step 1: Understand combining queries

   tax_query and meta_query are combined with AND logic by default when both are included in the query args.

2. Step 2: Correct structure

   Simply place both 'tax_query' and 'meta_query' as keys in the main query args array; no 'relation' is needed.

3. Final Answer:

   Combine tax_query and meta_query inside a single array without 'relation'. -> Option A

4. Quick Check:

   tax_query + meta_query default = AND [OK]

Hint: tax_query and meta_query default to AND logic [OK]

Common Mistakes:

• Adding unnecessary 'relation' => 'AND'
• Nesting queries inside one another
• Using 'relation' => 'OR' for AND logic