interface SelectInterface

interface SelectInterface extends ConditionInterface, AlterableInterface, ExtendableInterface, PlaceholderInterface {
    
    /* Alter accessors to expose the query data to alter hooks. */
    
    /**
     * Returns a reference to the fields array for this query.
     *
     * Because this method returns by reference, alter hooks may edit the fields
     * array directly to make their changes. If just adding fields, however, the
     * use of addField() is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $fields =& $query->getFields();
     * @endcode
     *
     * @return array
     *   A reference to the fields array structure.
     */
    public function &getFields();
    
    /**
     * Returns a reference to the expressions array for this query.
     *
     * Because this method returns by reference, alter hooks may edit the expressions
     * array directly to make their changes. If just adding expressions, however, the
     * use of addExpression() is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $fields =& $query->getExpressions();
     * @endcode
     *
     * @return array
     *   A reference to the expression array structure.
     */
    public function &getExpressions();
    
    /**
     * Returns a reference to the order by array for this query.
     *
     * Because this method returns by reference, alter hooks may edit the order-by
     * array directly to make their changes. If just adding additional ordering
     * fields, however, the use of orderBy() is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $fields =& $query->getOrderBy();
     * @endcode
     *
     * @return array
     *   A reference to the expression array structure.
     */
    public function &getOrderBy();
    
    /**
     * Returns a reference to the group-by array for this query.
     *
     * Because this method returns by reference, alter hooks may edit the group-by
     * array directly to make their changes. If just adding additional grouping
     * fields, however, the use of groupBy() is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $fields =& $query->getGroupBy();
     * @endcode
     *
     * @return array
     *   A reference to the group-by array structure.
     */
    public function &getGroupBy();
    
    /**
     * Returns a reference to the tables array for this query.
     *
     * Because this method returns by reference, alter hooks may edit the tables
     * array directly to make their changes. If just adding tables, however, the
     * use of the join() methods is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $tables =& $query->getTables();
     * @endcode
     *
     * @return array
     *   A reference to the tables array structure.
     */
    public function &getTables();
    
    /**
     * Returns a reference to the union queries for this query.
     *
     * This includes queries for UNION, UNION ALL, and UNION DISTINCT.
     *
     * Because this method returns by reference, alter hooks may edit the tables
     * array directly to make their changes. If just adding union queries,
     * however, the use of the union() method is preferred.
     *
     * Note that this method must be called by reference as well:
     *
     * @code
     * $fields =& $query->getUnion();
     * @endcode
     *
     * @return array
     *   A reference to the union query array structure.
     */
    public function &getUnion();
    
    /**
     * Escapes characters that work as wildcard characters in a LIKE pattern.
     *
     * @param $string
     *   The string to escape.
     *
     * @return string
     *   The escaped string.
     *
     * @see \Drupal\Core\Database\Connection::escapeLike()
     */
    public function escapeLike($string);
    
    /**
     * Escapes a field name string.
     *
     * Force all field names to be strictly alphanumeric-plus-underscore.
     * For some database drivers, it may also wrap the field name in
     * database-specific escape characters.
     *
     * @param string $string
     *   An unsanitized field name.
     *
     * @return string
     *   The sanitized field name string.
     */
    public function escapeField($string);
    
    /**
     * Compiles and returns an associative array of the arguments for this prepared statement.
     *
     * @param $queryPlaceholder
     *   When collecting the arguments of a subquery, the main placeholder
     *   object should be passed as this parameter.
     *
     * @return array
     *   An associative array of all placeholder arguments for this query.
     */
    public function getArguments(?PlaceholderInterface $queryPlaceholder = NULL);
    
    /* Query building operations */
    
    /**
     * Sets this query to be DISTINCT.
     *
     * @param $distinct
     *   TRUE to flag this query DISTINCT, FALSE to disable it.
     *
     * @return $this
     *   The called object.
     */
    public function distinct($distinct = TRUE);
    
    /**
     * Adds a field to the list to be SELECTed.
     *
     * @param $table_alias
     *   The name of the table from which the field comes, as an alias. Generally
     *   you will want to use the return value of join() here to ensure that it is
     *   valid.
     * @param $field
     *   The name of the field.
     * @param $alias
     *   The alias for this field. If not specified, one will be generated
     *   automatically based on the $table_alias and $field. The alias will be
     *   checked for uniqueness, so the requested alias may not be the alias
     *   that is assigned in all cases.
     *
     * @return string
     *   The unique alias that was assigned for this field.
     */
    public function addField($table_alias, $field, $alias = NULL);
    
    /**
     * Add multiple fields from the same table to be SELECTed.
     *
     * This method does not return the aliases set for the passed fields. In the
     * majority of cases that is not a problem, as the alias will be the field
     * name. However, if you do need to know the alias you can call getFields()
     * and examine the result to determine what alias was created. Alternatively,
     * simply use addField() for the few fields you care about and this method for
     * the rest.
     *
     * @param $table_alias
     *   The name of the table from which the field comes, as an alias. Generally
     *   you will want to use the return value of join() here to ensure that it is
     *   valid.
     * @param $fields
     *   An indexed array of fields present in the specified table that should be
     *   included in this query. If not specified, $table_alias.* will be generated
     *   without any aliases.
     *
     * @return $this
     *   The called object.
     */
    public function fields($table_alias, array $fields = []);
    
    /**
     * Adds an expression to the list of "fields" to be SELECTed.
     *
     * An expression can be any arbitrary string that is valid SQL. That includes
     * various functions, which may in some cases be database-dependent. This
     * method makes no effort to correct for database-specific functions.
     *
     * @param $expression
     *   The expression string. May contain placeholders.
     * @param $alias
     *   The alias for this expression. If not specified, one will be generated
     *   automatically in the form "expression_#". The alias will be checked for
     *   uniqueness, so the requested alias may not be the alias that is assigned
     *   in all cases.
     * @param $arguments
     *   Any placeholder arguments needed for this expression.
     *
     * @return string
     *   The unique alias that was assigned for this expression.
     */
    public function addExpression($expression, $alias = NULL, $arguments = []);
    
    /**
     * Default Join against another table in the database.
     *
     * This method is a convenience method for innerJoin().
     *
     * @param $table
     *   The table against which to join. May be a string or another SelectQuery
     *   object. If a query object is passed, it will be used as a subselect.
     *   Unless the table name starts with the database / schema name and a dot
     *   it will be prefixed.
     * @param $alias
     *   The alias for the table. In most cases this should be the first letter
     *   of the table, or the first letter of each "word" in the table.
     * @param $condition
     *   The condition on which to join this table. If the join requires values,
     *   this clause should use a named placeholder and the value or values to
     *   insert should be passed in the 4th parameter. For the first table joined
     *   on a query, this value is ignored as the first table is taken as the base
     *   table. The token %alias can be used in this string to be replaced with
     *   the actual alias. This is useful when $alias is modified by the database
     *   system, for example, when joining the same table more than once.
     * @param $arguments
     *   An array of arguments to replace into the $condition of this join.
     *
     * @return string
     *   The unique alias that was assigned for this table.
     */
    public function join($table, $alias = NULL, $condition = NULL, $arguments = []);
    
    /**
     * Inner Join against another table in the database.
     *
     * @param $table
     *   The table against which to join. May be a string or another SelectQuery
     *   object. If a query object is passed, it will be used as a subselect.
     *   Unless the table name starts with the database / schema name and a dot
     *   it will be prefixed.
     * @param $alias
     *   The alias for the table. In most cases this should be the first letter
     *   of the table, or the first letter of each "word" in the table.
     * @param $condition
     *   The condition on which to join this table. If the join requires values,
     *   this clause should use a named placeholder and the value or values to
     *   insert should be passed in the 4th parameter. For the first table joined
     *   on a query, this value is ignored as the first table is taken as the base
     *   table. The token %alias can be used in this string to be replaced with
     *   the actual alias. This is useful when $alias is modified by the database
     *   system, for example, when joining the same table more than once.
     * @param $arguments
     *   An array of arguments to replace into the $condition of this join.
     *
     * @return string
     *   The unique alias that was assigned for this table.
     */
    public function innerJoin($table, $alias = NULL, $condition = NULL, $arguments = []);
    
    /**
     * Left Outer Join against another table in the database.
     *
     * @param $table
     *   The table against which to join. May be a string or another SelectQuery
     *   object. If a query object is passed, it will be used as a subselect.
     *   Unless the table name starts with the database / schema name and a dot
     *   it will be prefixed.
     * @param $alias
     *   The alias for the table. In most cases this should be the first letter
     *   of the table, or the first letter of each "word" in the table.
     * @param $condition
     *   The condition on which to join this table. If the join requires values,
     *   this clause should use a named placeholder and the value or values to
     *   insert should be passed in the 4th parameter. For the first table joined
     *   on a query, this value is ignored as the first table is taken as the base
     *   table. The token %alias can be used in this string to be replaced with
     *   the actual alias. This is useful when $alias is modified by the database
     *   system, for example, when joining the same table more than once.
     * @param $arguments
     *   An array of arguments to replace into the $condition of this join.
     *
     * @return string
     *   The unique alias that was assigned for this table.
     */
    public function leftJoin($table, $alias = NULL, $condition = NULL, $arguments = []);
    
    /**
     * Join against another table in the database.
     *
     * This method does the "hard" work of queueing up a table to be joined against.
     * In some cases, that may include dipping into the Schema API to find the necessary
     * fields on which to join.
     *
     * @param $type
     *   The type of join. Typically one of INNER, LEFT OUTER, and RIGHT OUTER.
     * @param $table
     *   The table against which to join. May be a string or another SelectQuery
     *   object. If a query object is passed, it will be used as a subselect.
     *   Unless the table name starts with the database / schema name and a dot
     *   it will be prefixed.
     * @param $alias
     *   The alias for the table. In most cases this should be the first letter
     *   of the table, or the first letter of each "word" in the table. If omitted,
     *   one will be dynamically generated.
     * @param $condition
     *   The condition on which to join this table. If the join requires values,
     *   this clause should use a named placeholder and the value or values to
     *   insert should be passed in the 4th parameter. For the first table joined
     *   on a query, this value is ignored as the first table is taken as the base
     *   table. The token %alias can be used in this string to be replaced with
     *   the actual alias. This is useful when $alias is modified by the database
     *   system, for example, when joining the same table more than once.
     * @param $arguments
     *   An array of arguments to replace into the $condition of this join.
     *
     * @return string
     *   The unique alias that was assigned for this table.
     */
    public function addJoin($type, $table, $alias = NULL, $condition = NULL, $arguments = []);
    
    /**
     * Orders the result set by a given field.
     *
     * If called multiple times, the query will order by each specified field in the
     * order this method is called.
     *
     * If the query uses DISTINCT or GROUP BY conditions, fields or expressions
     * that are used for the order must be selected to be compatible with some
     * databases like PostgreSQL. The PostgreSQL driver can handle simple cases
     * automatically but it is suggested to explicitly specify them. Additionally,
     * when ordering on an alias, the alias must be added before orderBy() is
     * called.
     *
     * @param $field
     *   The field on which to order. The field is escaped for security so only
     *   valid field and alias names are possible. To order by an expression, add
     *   the expression with addExpression() first and then use the alias to order
     *   on.
     *
     *   Example:
     *   @code
     *   $query->addExpression('SUBSTRING([thread], 1, (LENGTH([thread]) - 1))', 'order_field');
     *   $query->orderBy('order_field', 'ASC');
     *   @endcode
     * @param $direction
     *   The direction to sort. Legal values are "ASC" and "DESC". Any other value
     *   will be converted to "ASC".
     *
     * @return $this
     *   The called object.
     */
    public function orderBy($field, $direction = 'ASC');
    
    /**
     * Orders the result set by a random value.
     *
     * This may be stacked with other orderBy() calls. If so, the query will order
     * by each specified field, including this one, in the order called. Although
     * this method may be called multiple times on the same query, doing so
     * is not particularly useful.
     *
     * Note: The method used by most drivers may not scale to very large result
     * sets. If you need to work with extremely large data sets, you may create
     * your own database driver by subclassing off of an existing driver and
     * implementing your own randomization mechanism. See
     *
     * http://jan.kneschke.de/projects/mysql/order-by-rand/
     *
     * for an example of such an alternate sorting mechanism.
     *
     * @return $this
     *   The called object
     */
    public function orderRandom();
    
    /**
     * Restricts a query to a given range in the result set.
     *
     * If this method is called with no parameters, will remove any range
     * directives that have been set.
     *
     * @param $start
     *   The first record from the result set to return. If NULL, removes any
     *   range directives that are set.
     * @param $length
     *   The number of records to return from the result set.
     *
     * @return $this
     *   The called object.
     */
    public function range($start = NULL, $length = NULL);
    
    /**
     * Add another Select query to UNION to this one.
     *
     * Union queries consist of two or more queries whose
     * results are effectively concatenated together. Queries
     * will be UNIONed in the order they are specified, with
     * this object's query coming first. Duplicate columns will
     * be discarded. All forms of UNION are supported, using
     * the second '$type' argument.
     *
     * Note: All queries UNIONed together must have the same
     * field structure, in the same order. It is up to the
     * caller to ensure that they match properly. If they do
     * not, an SQL syntax error will result.
     *
     * @param $query
     *   The query to UNION to this query.
     * @param $type
     *   The type of UNION to add to the query. Defaults to plain
     *   UNION.
     *
     * @return $this
     *   The called object.
     */
    public function union(SelectInterface $query, $type = '');
    
    /**
     * Groups the result set by the specified field.
     *
     * @param $field
     *   The field on which to group. This should be the field as aliased.
     *
     * @return $this
     *   The called object.
     */
    public function groupBy($field);
    
    /**
     * Get the equivalent COUNT query of this query as a new query object.
     *
     * @return \Drupal\Core\Database\Query\SelectInterface
     *   A new SelectQuery object with no fields or expressions besides COUNT(*).
     */
    public function countQuery();
    
    /**
     * Indicates if preExecute() has already been called on that object.
     *
     * @return bool
     *   TRUE is this query has already been prepared, FALSE otherwise.
     */
    public function isPrepared();
    
    /**
     * Generic preparation and validation for a SELECT query.
     *
     * @return bool
     *   TRUE if the validation was successful, FALSE if not.
     */
    public function preExecute(?SelectInterface $query = NULL);
    
    /**
     * Runs the query against the database.
     *
     * @return \Drupal\Core\Database\StatementInterface|null
     *   A prepared statement, or NULL if the query is not valid.
     */
    public function execute();
    
    /**
     * Helper function to build most common HAVING conditional clauses.
     *
     * This method can take a variable number of parameters. If called with two
     * parameters, they are taken as $field and $value with $operator having a value
     * of IN if $value is an array and = otherwise.
     *
     * @param $field
     *   The name of the field to check. If you would like to add a more complex
     *   condition involving operators or functions, use having().
     * @param $value
     *   The value to test the field against. In most cases, this is a scalar. For more
     *   complex options, it is an array. The meaning of each element in the array is
     *   dependent on the $operator.
     * @param $operator
     *   The comparison operator, such as =, <, or >=. It also accepts more complex
     *   options such as IN, LIKE, or BETWEEN. Defaults to IN if $value is an array
     *   = otherwise.
     *
     * @return \Drupal\Core\Database\Query\ConditionInterface
     *   The called object.
     */
    public function havingCondition($field, $value = NULL, $operator = NULL);
    
    /**
     * Gets a list of all conditions in the HAVING clause.
     *
     * This method returns by reference. That allows alter hooks to access the
     * data structure directly and manipulate it before it gets compiled.
     *
     * @return array
     *   An array of conditions.
     *
     * @see \Drupal\Core\Database\Query\ConditionInterface::conditions()
     */
    public function &havingConditions();
    
    /**
     * Gets a list of all values to insert into the HAVING clause.
     *
     * @return array
     *   An associative array of placeholders and values.
     */
    public function havingArguments();
    
    /**
     * Adds an arbitrary HAVING clause to the query.
     *
     * @param $snippet
     *   A portion of a HAVING clause as a prepared statement. It must use named
     *   placeholders, not ? placeholders.
     * @param $args
     *   (optional) An associative array of arguments.
     *
     * @return $this
     */
    public function having($snippet, $args = []);
    
    /**
     * Compiles the HAVING clause for later retrieval.
     *
     * @param $connection
     *   The database connection for which to compile the clause.
     */
    public function havingCompile(Connection $connection);
    
    /**
     * Sets a condition in the HAVING clause that the specified field be NULL.
     *
     * @param $field
     *   The name of the field to check.
     *
     * @return $this
     */
    public function havingIsNull($field);
    
    /**
     * Sets a condition in the HAVING clause that the specified field be NOT NULL.
     *
     * @param $field
     *   The name of the field to check.
     *
     * @return $this
     */
    public function havingIsNotNull($field);
    
    /**
     * Sets a HAVING condition that the specified subquery returns values.
     *
     * @param \Drupal\Core\Database\Query\SelectInterface $select
     *   The subquery that must contain results.
     *
     * @return $this
     */
    public function havingExists(SelectInterface $select);
    
    /**
     * Sets a HAVING condition that the specified subquery returns no values.
     *
     * @param \Drupal\Core\Database\Query\SelectInterface $select
     *   The subquery that must contain results.
     *
     * @return $this
     */
    public function havingNotExists(SelectInterface $select);
    
    /**
     * Clone magic method.
     *
     * Select queries have dependent objects that must be deep-cloned.  The
     * connection object itself, however, should not be cloned as that would
     * duplicate the connection itself.
     */
    public function __clone();
    
    /**
     * Add FOR UPDATE to the query.
     *
     * FOR UPDATE prevents the rows retrieved by the SELECT statement from being
     * modified or deleted by other transactions until the current transaction
     * ends. Other transactions that attempt UPDATE, DELETE, or SELECT FOR UPDATE
     * of these rows will be blocked until the current transaction ends.
     *
     * @param $set
     *   IF TRUE, FOR UPDATE will be added to the query, if FALSE then it won't.
     *
     * @return \Drupal\Core\Database\Query\ConditionInterface
     *   The called object.
     */
    public function forUpdate($set = TRUE);
    
    /**
     * Returns a string representation of how the query will be executed in SQL.
     *
     * @return string
     *   The Select Query object expressed as a string.
     */
    public function __toString();

}