The next step is to actually create the database table. Rather than executing an SQL query directly, we'll use the dbDelta function in wp-admin/includes/upgrade.php (we'll have to load this file, as it is not loaded by default). The dbDelta function examines the current table structure, compares it to the desired table structure, and either adds or modifies the table as necessary, so it can be very handy for updates (see wp-admin/upgrade-schema.php for more examples of how to use dbDelta). Note that the dbDelta function is rather picky, however. For instance:
- You must put each field on its own line in your SQL statement.
- You must have two spaces between the words PRIMARY KEY and the definition of your primary key.
- You must use the key word KEY rather than its synonym INDEX and you must include at least one KEY.
- KEY must be followed by a SINGLE SPACE then the key name then a space then open parenthesis with the field name then a closed parenthesis.
- You must not use a