code: public function addCheck($name, $table, $expression)
      {
          return 'ALTER TABLE ' . $this->db->quoteTableName($table) . ' ADD CONSTRAINT '
              . $this->db->quoteColumnName($name) . ' CHECK (' . $this->db->quoteSql($expression) . ')';
      }
docs: Creates a SQL command for adding a check constraint to an existing table.
  @param string $name the name of the check constraint.
  The name will be properly quoted by the method.
  @param string $table the table that the check constraint will be added to.
  The name will be properly quoted by the method.
  @param string $expression the SQL of the `CHECK` constraint.
  @return string the SQL statement for adding a check constraint to an existing table.
  @since 2.0.13