interface TablesInterface

interface TablesInterface {
    
    /**
     * Adds a field to a database query.
     *
     * @param string $field
     *   If it doesn't contain a dot, then an entity base field name. If it
     *   contains a dot, then either field name dot field column or field name dot
     *   delta dot field column. Delta can be a numeric value or a "%delta" for
     *   any value.
     * @param string $type
     *   Join type, can either be INNER or LEFT.
     * @param string $langcode
     *   The language code the field values are to be queried in.
     *
     * @return string
     *   The return value is a string containing the alias of the table, a dot
     *   and the appropriate SQL column as passed in. This allows the direct use
     *   of this in a query for a condition or sort.
     *
     * @throws \Drupal\Core\Entity\Query\QueryException
     *   If $field specifies an invalid relationship.
     */
    public function addField($field, $type, $langcode);
    
    /**
     * Determines whether the given field is case sensitive.
     *
     * This information can only be provided after it was added with addField().
     *
     * @param string $field_name
     *   The name of the field.
     *
     * @return bool|null
     *   TRUE if the field is case sensitive, FALSE if not. Returns NULL when the
     *   field did not define if it is case sensitive or not.
     */
    public function isFieldCaseSensitive($field_name);

}