What Is meta_id In wp_postmeta?

Question

I am trying to add some data in WordPress Custom Field and via adding more direct records/data in wp_postmeta table via SQL query. There are four column as mentioned below...

• 'meta_id' - A unique id for each entry.
• 'post_id' - The ID of the post for this metadata.
• 'meta_key' - The name of the 'key'.
• 'meta_value' - The value associated with the key.

Now I am using the below SQL query to add some more records/data.

$INSERTING_DATA = "INSERT INTO `wp_postmeta` (`meta_id`, `post_id`, `meta_key`, `meta_value`) values ('XXXXXXXXX', 'WordPress_Post_ID_No', 'WordPress_Post_Custom_Field_Name', 'WordPress_Post_Custom_Field_Value')";

So here I am able to add all my data but I want to know that what to add in meta_id column ? Is that auto increment value so I have to leave that value and should I use below SQL query...???

$INSERTING_DATA = "INSERT INTO `wp_postmeta` (`post_id`, `meta_key`, `meta_value`) values ('WordPress_Post_ID_No', 'WordPress_Post_Custom_Field_Name', 'WordPress_Post_Custom_Field_Value')";

So Now tell me which one is correct and Ok to use. First or second...??? Also describe me that what is meta_id in this table?

Answer 1

meta_id in postmeta table is just an AUTO_INCREMENT id for the table, you can easily inspect that:

So, your guess is correct, you can leave it.

EDIT

Avoid raw SQL statements and introduce $wpdb for SQL purposes. And for postmeta insertion you can see the following tutorial I found a best one:

• Reusable Custom Meta Boxes - Code.TutsPlus.com

Answer 2

You should not be using direct SQL. Consider creating a PHP script that loads WordPress core functions and uses them (see https://stackoverflow.com/questions/9101503/include-wordpress-core-into-own-scripts#answer-9126230 for getting an idea how to do that).

• add_post_meta

• update_post_meta

But if you do want to create custom SQL (if you are asking the question you are asking I highly do not recommend it), you should probably get more information on postmeta table before doing so. Let me cover the topic for you.

First of all, let's get some overview of the table:

mysql> describe wp40.wp_postmeta;
+------------+---------------------+------+-----+---------+----------------+
| Field      | Type                | Null | Key | Default | Extra          |
+------------+---------------------+------+-----+---------+----------------+
| meta_id    | bigint(20) unsigned | NO   | PRI | NULL    | auto_increment |
| post_id    | bigint(20) unsigned | NO   | MUL | 0       |                |
| meta_key   | varchar(255)        | YES  | MUL | NULL    |                |
| meta_value | longtext            | YES  |     | NULL    |                |
+------------+---------------------+------+-----+---------+----------------+
4 rows in set (0,08 sec)

From that you can see that meta_id is auto_increment and thus MySQL will figure out itself what value it should add. Passing simple 0 instead of real meta_id is enough.

post_id refers back to the post to which the meta is associated. Default is 0 but you should pass a real post_id so you can see the meta in the custom fields editor on the post editing screen.

meta_key is the name of a meta. Pay attention, using a name starting with underscore eg.: _hidden_meta will hide the meta from custom field editor on edit screen.

meta_value is a longtext and can hold any text you need. But pass it strings only! (in case of an array of other objects, you can serialize the text).

But once again, consider using add_post_meta or update_post_meta functions.