How to check main blog in a multisite using if statement?

Question

I want to create one extra table filed if it is multisite's main blog (While plugin activation).

I mean like this

if (main blog) {
  execute this sql;
}
else {
  execute this sql
}

PS: This is the code for "execute this sql".

If child blog:

$sql = "CREATE TABLE tablename (
                  id bigint(20) NOT NULL AUTO_INCREMENT,
                  uid bigint(20) NOT NULL,
                  type VARCHAR(256) NOT NULL,
                  data TEXT NOT NULL,
                  credits bigint(20) NOT NULL,
                  timestamp bigint(20) NOT NULL,
                  UNIQUE KEY id (id)
                );";

If main blog:

$sql = "CREATE TABLE tablename (
              id bigint(20) NOT NULL AUTO_INCREMENT,
              uid bigint(20) NOT NULL,
              type VARCHAR(256) NOT NULL,
              data TEXT NOT NULL,
              credits bigint(20) NOT NULL,
                      globalcredits bigint(20) NOT NULL,
              timestamp bigint(20) NOT NULL,
              UNIQUE KEY id (id)
            );";

Can anyone help me?

Answer 1

You can use is_main_site conditional tag like this:

if (is_main_site()) {
  execute this sql;
}
else {
  execute this sql
}

Answer 2

Check for the $blogid. Main site is 1.

global $wpdb;

$mainblog = $wpdb->blogid;

if ($mainblog === 1) {
   execute this sql;
}
else {
    execute this sql
}