title: Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '='
body: <p>Error message on MySql:</p>
  
  <pre><code>Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '='
  </code></pre>
  
  <p>I have gone through several other posts and was not able to solve this problem.
  The part affected is something similar to this:</p>
  
  <pre><code>CREATE TABLE users (
      userID INT UNSIGNED NOT NULL AUTO_INCREMENT,
      firstName VARCHAR(24) NOT NULL,
      lastName VARCHAR(24) NOT NULL,
      username VARCHAR(24) NOT NULL,
      password VARCHAR(40) NOT NULL,
      PRIMARY KEY (userid)
  ) ENGINE = INNODB CHARACTER SET utf8 COLLATE utf8_unicode_ci;
  
  CREATE TABLE products (
      productID INT UNSIGNED NOT NULL AUTO_INCREMENT,
      title VARCHAR(104) NOT NULL,
      picturePath VARCHAR(104) NULL,
      pictureThumb VARCHAR(104) NULL,
      creationDate DATE NOT NULL,
      closeDate DATE NULL,
      deleteDate DATE NULL,
      varPath VARCHAR(104) NULL,
      isPublic TINYINT(1) UNSIGNED NOT NULL DEFAULT '1',
      PRIMARY KEY (productID)
  ) ENGINE = INNODB CHARACTER SET utf8 COLLATE utf8_unicode_ci;
  
  CREATE TABLE productUsers (
      productID INT UNSIGNED NOT NULL,
      userID INT UNSIGNED NOT NULL,
      permission VARCHAR(16) NOT NULL,
      PRIMARY KEY (productID,userID),
      FOREIGN KEY (productID) REFERENCES products (productID) ON DELETE RESTRICT ON UPDATE NO ACTION,
      FOREIGN KEY (userID) REFERENCES users (userID) ON DELETE RESTRICT ON UPDATE NO ACTION
  ) ENGINE = INNODB CHARACTER SET utf8 COLLATE utf8_unicode_ci;
  </code></pre>
  
  <p>The stored procedure I'm using is this:</p>
  
  <pre><code>CREATE PROCEDURE updateProductUsers (IN rUsername VARCHAR(24),IN rProductID INT UNSIGNED,IN rPerm VARCHAR(16))
  BEGIN
      UPDATE productUsers
          INNER JOIN users
          ON productUsers.userID = users.userID
          SET productUsers.permission = rPerm
          WHERE users.username = rUsername
          AND productUsers.productID = rProductID;
  END
  </code></pre>
  
  <p>I was testing with php, but the same error is given with SQLyog.
  I have also tested recreating the entire DB but to no good.</p>
  
  <p>Any help will be much appreciated.</p>