Why only the second?
Because dbDelta() supports CREATE TABLE table_name format only. I.e. Exactly “CREATE TABLE” followed by (one space and) the table name.
More specifically, dbDelta() uses this regular expression pattern: CREATE TABLE ([^ ]*) when parsing the queries into an array indexed by the table name; i.e. array( 'table_1' => 'query', 'table_2' => 'query', ... ).
Here’s the relevant code:
$cqueries = array(); // Creation Queries
...
// Create a tablename index for an array ($cqueries) of queries
foreach ( $queries as $qry ) {
if ( preg_match( '|CREATE TABLE ([^ ]*)|', $qry, $matches ) ) {
$cqueries[ trim( $matches[1], '`' ) ] = $qry;
$for_update[ $matches[1] ] = 'Created table ' . $matches[1];
}
...
}
So in the case of CREATE TABLE IF NOT EXISTS table_name, the table name is (seen as) IF and not table_name due to the regular expression pattern:
preg_match( '|CREATE TABLE ([^ ]*)|', 'CREATE TABLE IF NOT EXISTS table_name', $matches );
var_dump( $matches );
/* Output:
array(2) {
[0]=>
string(15) "CREATE TABLE IF"
[1]=>
string(2) "IF"
}
*/
preg_match( '|CREATE TABLE ([^ ]*)|', 'CREATE TABLE table_name', $matches );
var_dump( $matches );
/* Output:
array(2) {
[0]=>
string(23) "CREATE TABLE table_name"
[1]=>
string(10) "table_name"
}
*/
And in your case, both queries do match that pattern, but since the table names are both (seen as) IF, the first/previous array item ($queries['IF']) is then overridden. Hence only the second table (the one in the final value of $queries['IF']) gets created.
And WooCommerce actually do not have CREATE TABLE IF NOT EXISTS in their code:
Possible Solution when using the CREATE TABLE IF NOT EXISTS table_name format
Call dbDelta() for each of the queries, as in @FahamShaikh’s answer:
$queries = [ // array of queries
"CREATE TABLE IF NOT EXISTS " . $wpdb->prefix . "test1 ...",
"CREATE TABLE IF NOT EXISTS " . $wpdb->prefix . "test2 ...",
];
foreach ( $queries as $sql ) {
dbDelta( $sql );
}
Or:
dbDelta( "CREATE TABLE IF NOT EXISTS " . $wpdb->prefix . "test1 ..." );
dbDelta( "CREATE TABLE IF NOT EXISTS " . $wpdb->prefix . "test2 ..." );