public function Select::__toString in Drupal 8

Same name and namespace in other branches

1. 9 core/lib/Drupal/Core/Database/Query/Select.php \Drupal\Core\Database\Query\Select::__toString()

Implements PHP magic __toString method to convert the query to a string.

The toString operation is how we compile a query object to a prepared statement.

Return value

string A prepared statement query string for this object.

Overrides Query::__toString

File

core/lib/Drupal/Core/Database/Query/Select.php, line 795

Class

Select

Query builder for SELECT statements.

Namespace

Drupal\Core\Database\Query

Code

public function __toString() {

  // For convenience, we compile the query ourselves if the caller forgot
  // to do it. This allows constructs like "(string) $query" to work. When
  // the query will be executed, it will be recompiled using the proper
  // placeholder generator anyway.
  if (!$this
    ->compiled()) {
    $this
      ->compile($this->connection, $this);
  }

  // Create a sanitized comment string to prepend to the query.
  $comments = $this->connection
    ->makeComment($this->comments);

  // SELECT
  $query = $comments . 'SELECT ';
  if ($this->distinct) {
    $query .= 'DISTINCT ';
  }

  // FIELDS and EXPRESSIONS
  $fields = [];
  foreach ($this->tables as $alias => $table) {
    if (!empty($table['all_fields'])) {
      $fields[] = $this->connection
        ->escapeAlias($alias) . '.*';
    }
  }
  foreach ($this->fields as $field) {

    // Note that $field['table'] holds the table alias.
    // @see \Drupal\Core\Database\Query\Select::addField
    $table = isset($field['table']) ? $this->connection
      ->escapeAlias($field['table']) . '.' : '';

    // Always use the AS keyword for field aliases, as some
    // databases require it (e.g., PostgreSQL).
    $fields[] = $table . $this->connection
      ->escapeField($field['field']) . ' AS ' . $this->connection
      ->escapeAlias($field['alias']);
  }
  foreach ($this->expressions as $expression) {
    $fields[] = $expression['expression'] . ' AS ' . $this->connection
      ->escapeAlias($expression['alias']);
  }
  $query .= implode(', ', $fields);

  // FROM - We presume all queries have a FROM, as any query that doesn't won't need the query builder anyway.
  $query .= "\nFROM";
  foreach ($this->tables as $table) {
    $query .= "\n";
    if (isset($table['join type'])) {
      $query .= $table['join type'] . ' JOIN ';
    }

    // If the table is a subquery, compile it and integrate it into this query.
    if ($table['table'] instanceof SelectInterface) {

      // Run preparation steps on this sub-query before converting to string.
      $subquery = $table['table'];
      $subquery
        ->preExecute();
      $table_string = '(' . (string) $subquery . ')';
    }
    else {
      $table_string = $this->connection
        ->escapeTable($table['table']);

      // Do not attempt prefixing cross database / schema queries.
      if (strpos($table_string, '.') === FALSE) {
        $table_string = '{' . $table_string . '}';
      }
    }

    // Don't use the AS keyword for table aliases, as some
    // databases don't support it (e.g., Oracle).
    $query .= $table_string . ' ' . $this->connection
      ->escapeAlias($table['alias']);
    if (!empty($table['condition'])) {
      $query .= ' ON ' . (string) $table['condition'];
    }
  }

  // WHERE
  if (count($this->condition)) {

    // There is an implicit string cast on $this->condition.
    $query .= "\nWHERE " . $this->condition;
  }

  // GROUP BY
  if ($this->group) {
    $query .= "\nGROUP BY " . implode(', ', $this->group);
  }

  // HAVING
  if (count($this->having)) {

    // There is an implicit string cast on $this->having.
    $query .= "\nHAVING " . $this->having;
  }

  // UNION is a little odd, as the select queries to combine are passed into
  // this query, but syntactically they all end up on the same level.
  if ($this->union) {
    foreach ($this->union as $union) {
      $query .= ' ' . $union['type'] . ' ' . (string) $union['query'];
    }
  }

  // ORDER BY
  if ($this->order) {
    $query .= "\nORDER BY ";
    $fields = [];
    foreach ($this->order as $field => $direction) {
      $fields[] = $this->connection
        ->escapeField($field) . ' ' . $direction;
    }
    $query .= implode(', ', $fields);
  }

  // RANGE
  // There is no universal SQL standard for handling range or limit clauses.
  // Fortunately, all core-supported databases use the same range syntax.
  // Databases that need a different syntax can override this method and
  // do whatever alternate logic they need to.
  if (!empty($this->range)) {
    $query .= "\nLIMIT " . (int) $this->range['length'] . " OFFSET " . (int) $this->range['start'];
  }
  if ($this->forUpdate) {
    $query .= ' FOR UPDATE';
  }
  return $query;
}