Using WHERE on a WP_Query

If I understood correctly, you need something like the following:

$args = array(
    'post_type' => 'book',
    'posts_per_page' => -1,
    'meta_key' => 'subject',
    'meta_value' => YOUR_SUBJECT_PAGE_TITLE,
);
$books = new WP_Query($args);

Is this what you’re trying to achieve?

Also, please have a look at WP_Query.

Related Posts:

  1. Way to include posts both with & without certain meta_key in args for wp_query?
  2. How to Access Global $multipage or Global $numpages outside the loop?
  3. How can I use WP-CLI commands without –allow-root
  4. Calling a wp_query $posts causes a 500 error
  5. WP_query taxonomy + get all posts with two terms from same taxonomy
  6. Merging a complex query with post_rewind and splitting posts into two columns
  7. How do I create my own nested meta_query using posts_where / posts_join?
  8. meta_query not working properly
  9. Best Practice For Querying Grandchildren?
  10. Filter wp_query to search post title in function
  11. Two queries on the same page with pagination
  12. Using tax_query reverses my post_type argument in a custom WP_Query
  13. Best approach to create Hot and Trending sections
  14. creating wp query with posts with specific category
  15. $wp_query->current_post restarts from zero on paged pages
  16. get complex results set according to category structure
  17. wp_get_post_terms of cpt but not duplicates if they are used more than once in the loop
  18. How to prevent queried posts from being added to cache?
  19. Setup of taxonomy term template pages
  20. Ignore post by meta value in the main query
  21. Display posts in 3 days chunk
  22. How to make orderby ‘meta_value_num’ OPTIONAL?
  23. WP_Query’s “request” SQL Query
  24. How to do a query on custom taxonomies that is uncategorised?
  25. is_search was called incorrectly
  26. Empty tax_query array returns an empty array
  27. How can I query posts with newly uploaded images?
  28. Conditional arguments WP_Query for post custom fields
  29. Sorting By Custom Posts With Attachments
  30. Random loop with code to prevent duplicate output returns no output at all from time to time
  31. Single meta_query query using OR instead of AND in request’s WHERE statement
  32. How to choose between hooking into per_get_posts or into parse_query
  33. Woocommerce returns Product post_status as published even tho it is in status draft
  34. remove query arg from url after set query
  35. How to loop for every result found in the_content() when using the search query?
  36. How can I fix: “Notice: Undefined offset: 0”?
  37. SQL: What is wrong with the following query (generated by WordPress WP_Query, ordering prices)
  38. Order By table field comment_status in WordPress > 4.0
  39. Slow WP_Query for custom post type
  40. Most commented last 24h, week, month, year and all time – posts_where
  41. WP_Query Pagination on multiple-loop page breaks WP or doesn’t show up
  42. Why isn’t my `meta_query` array functioning properly?
  43. Using hook to use DISTINCT in a wp_query
  44. Overwrite YoastSEO meta-tags with another page’s [closed]
  45. Import wp users via one click demo option
  46. How to restrict the search fields for a specific post type
  47. WP_query sorting can’t sort danish letters (æ, ø, å)
  48. Dynamic User Id
  49. Slow queries on a huge database
  50. Pagination links missing for first link (1) and previous button? How to get pagination links to work?
  51. Multisite pagination issue by multi query archive 404
  52. Query with relation and one without relation using multiple taxonomies?
  53. Automatically Query Parent Taxonomy
  54. Hide elements outside loop based on query
  55. WP Query crashes on more than ~ 2000 posts
  56. different for loop if screen resolution < 1000px
  57. insert value from html into data base with wordpress
  58. Debugging wp_query orderby for taxonomy
  59. Get all posts which was posted on X Days WordPress
  60. Pagination is not working with custom query inside a homepage template
  61. How to load a script code only in posts?
  62. Display posts with specific value first in query
  63. wp_query comment and meta query
  64. Modify query posts
  65. I need to run a AJAX Fuction from within a WP_Query but only works on first item
  66. How to change tag based on metabox value within $wp_query
  67. What’s missing in this wp_query and meta_query
  68. Tax Query on product_cat using NOT IN as operator does not exclude that category
  69. How to use the Term Object from a custom select field in a query
  70. Random users always showing same 8 users
  71. meta_query order by date present -> future then show null
  72. whether a nonce is required for get type and get_query_var?
  73. Wp-query and column blocks
  74. Multi line of $wpdb->query just run 1 time and end the loop right after
  75. Sort posts on custom field AND after that sort on date?
  76. Get last child of given page by ID
  77. How to query users by post count no less than 10
  78. display the children of the post using the current page as the main parent
  79. Display 3 levels of categories on page
  80. Showing most popular post of week
  81. Related Post by Tags Code
  82. In Product Category archives how to show Posts having same/similar prod_cat slug structure?
  83. Display three sequential posts on each page load, without repeating previous
  84. Find by post_meta, then sort by post_meta, then sort by date (wp_posts)
  85. previous_posts_link not working in WordPress pagination
  86. Eliminate typical pages on search page, turn it into ajax search with “infinite” sized single page
  87. Optimising amount of calls to custom fields
  88. The sorting of posts by a meta_query with two keys fails while separated as single queries it works
  89. Hierarchical List Pages as a table
  90. WP_Query with several meta_query-statements and order by meta_value
  91. query_posts, oderby meta_value & print “future” posts
  92. Second wp_query doesn’t appear to be working
  93. difference between methods of query
  94. post__in not recognizing multiple IDs
  95. Related posts with WP_Query
  96. Custom WP_query in Jnews theme returns thousands of posts
  97. wp_query loop with compare operator simply not working, why?
  98. How to get all post_id and meta_value using meta_key in wp_postmeta table
  99. List categories using WP_Query
  100. WP Query – Show custom posts only if user contain some user meta