How to Efficiently Query WordPress Posts with Multiple Categories

If you’re working with WordPress and need to retrieve posts that belong to multiple categories, it’s essential to understand the different syntaxes available for the WP_Query object. In this discussion, we’ll explore three syntaxes and clarify their differences, helping you choose the most efficient method for your needs.

Understanding the Goal

All three syntaxes discussed aim to retrieve posts that belong to both categories 76 and 78, emphasizing the intersection of categories rather than a broader ‘OR’ condition.

Syntax 1



$wp_query = new WP_Query(array(
    'post_type' => 'post',
    'tax_query' => array(
        'relation' => 'AND',
        array(
            'taxonomy' => 'category',
            'field' => 'id',
            'terms' => array(78),
            'operator' => 'IN',
        ),
        array(
            'taxonomy' => 'category',
            'field' => 'id',
            'terms' => array(76),
            'operator' => 'IN',
        ),
    ),
));

Syntax 2

$wp_query = new WP_Query(array(

‘post_type’ => ‘post’,

‘tax_query’ => array(

array(

‘taxonomy’ => ‘category’,

‘field’ => ‘id’,

‘terms’ => array(76, 78),

‘operator’ => ‘AND’,

));

Syntax 3

$wp_query = new WP_Query(array(

‘post_type’ => ‘post’,

‘category__and’ => array(76, 78),

));

Efficiency Comparison

The discussion points out that all three syntaxes achieve the same result, but there are nuances in their efficiency and usage.

Syntax 1: Verbosity

Syntax 1 is considered less efficient due to its verbosity. It involves more typing and utilizes unnecessary IN clauses when a single clause would suffice.

Syntax 2: Compact and Preferred

Syntax 2 is a preferred method for many developers. It provides a more concise way of expressing the same query and is efficient in terms of both readability and performance.

Syntax 3: Backward Compatibility

Syntax 3, using category__and, exists for backward compatibility and ease of use. However, it is noted that top-level named conditions like category__and are less flexible and more limiting compared to their tax_query equivalents.

Why Three Ways?

The discussion sheds light on the reasons behind having three ways to achieve the same goal:

Syntax 1: Offers verbosity for defining conditions.
Syntax 2: A preferred and concise method with additional parameters for performance constraints.
Syntax 3: Exists for backward compatibility and ease of use but is less flexible, especially for custom taxonomies.

Additional Considerations

The discussion also brings up important points to consider:

The include_children parameter is TRUE by default in tax_query.
Using category__and with a custom taxonomy may have limitations due to when Tax_Query was introduced.

Conclusion

In conclusion, when querying WordPress posts with multiple categories, Syntax 2 stands out as a concise and efficient method. However, understanding the differences and considerations provided for each syntax empowers you to make informed choices based on your specific requirements.

WPscience