Tax queries and meta queries in Wordpress

Introduction

Tax queries and meta queries help you find posts based on categories, tags, or custom fields. They make your website show exactly what visitors want to see.

You want to show posts from a specific category or tag on a page.

You need to filter posts by custom fields like price or color.

You want to combine filters, like posts in a category AND with a certain custom field value.

You want to build a search that looks for posts with specific tags and meta data.

You want to create a custom list of posts based on user choices.

Syntax

Wordpress

$query = new WP_Query([
  'tax_query' => [
    [
      'taxonomy' => 'category',
      'field' => 'slug',
      'terms' => ['news', 'updates'],
      'operator' => 'IN'
    ]
  ],
  'meta_query' => [
    [
      'key' => 'price',
      'value' => 100,
      'compare' => '>=',
      'type' => 'NUMERIC'
    ]
  ]
]);

tax_query filters posts by taxonomy terms like categories or tags.

meta_query filters posts by custom fields (meta data) like price or color.

Examples

Find posts in the 'news' category.

Wordpress

$query = new WP_Query([
  'tax_query' => [
    [
      'taxonomy' => 'category',
      'field' => 'slug',
      'terms' => ['news']
    ]
  ]
]);

Find posts where the custom field 'color' equals 'blue'.

Wordpress

$query = new WP_Query([
  'meta_query' => [
    [
      'key' => 'color',
      'value' => 'blue',
      'compare' => '='
    ]
  ]
]);

Find posts tagged 'featured' with a rating of 4 or higher.

Wordpress

$query = new WP_Query([
  'tax_query' => [
    [
      'taxonomy' => 'post_tag',
      'field' => 'slug',
      'terms' => ['featured']
    ]
  ],
  'meta_query' => [
    [
      'key' => 'rating',
      'value' => 4,
      'compare' => '>='
    ]
  ]
]);

Sample Program

This code finds posts in the 'news' category that have a custom field 'featured' set to 'yes'. It prints the titles of these posts or says no posts found.

Wordpress

<?php
$args = [
  'post_type' => 'post',
  'tax_query' => [
    [
      'taxonomy' => 'category',
      'field' => 'slug',
      'terms' => ['news']
    ]
  ],
  'meta_query' => [
    [
      'key' => 'featured',
      'value' => 'yes',
      'compare' => '='
    ]
  ]
];
$query = new WP_Query($args);

if ($query->have_posts()) {
  while ($query->have_posts()) {
    $query->the_post();
    echo get_the_title() . "\n";
  }
} else {
  echo "No posts found.\n";
}
wp_reset_postdata();
?>

Important Notes

Always use wp_reset_postdata() after custom queries to avoid conflicts.

You can combine multiple taxonomies and meta queries using arrays for complex filters.

Use operator in tax queries to control how terms are matched (e.g., IN, NOT IN).

Summary

Tax queries filter posts by categories, tags, or custom taxonomies.

Meta queries filter posts by custom fields (meta data).

Combining tax and meta queries helps create precise post filters.

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