Implemented Statement::fetch(PDO::FETCH_COLUMN) in non-PDO driveres

Fixes #2953.

lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php

@@ -216,6 +216,9 @@ class DB2Statement implements \IteratorAggregate, Statement
 
         $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
         switch ($fetchMode) {
+            case \PDO::FETCH_COLUMN:
+                return $this->fetchColumn();
+
             case \PDO::FETCH_BOTH:
                 return db2_fetch_both($this->_stmt);
             case \PDO::FETCH_ASSOC:

lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php

@@ -272,6 +272,12 @@ class MysqliStatement implements \IteratorAggregate, Statement
             return false;
         }
 
+        $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
+
+        if ($fetchMode === PDO::FETCH_COLUMN) {
+            return $this->fetchColumn();
+        }
+
         $values = $this->_fetch();
         if (null === $values) {
             return false;
@@ -281,8 +287,6 @@ class MysqliStatement implements \IteratorAggregate, Statement
             throw new MysqliException($this->_stmt->error, $this->_stmt->sqlstate, $this->_stmt->errno);
         }
 
-        $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
-
         switch ($fetchMode) {
             case PDO::FETCH_NUM:
                 return $values;

lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php

@@ -387,6 +387,10 @@ class OCI8Statement implements IteratorAggregate, Statement
 
         $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
 
+        if ($fetchMode === PDO::FETCH_COLUMN) {
+            return $this->fetchColumn();
+        }
+
         if (PDO::FETCH_OBJ == $fetchMode) {
             return oci_fetch_object($this->_sth);
         }

lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php

@@ -203,6 +203,9 @@ class SQLAnywhereStatement implements IteratorAggregate, Statement
         $fetchMode = $fetchMode ?: $this->defaultFetchMode;
 
         switch ($fetchMode) {
+            case PDO::FETCH_COLUMN:
+                return $this->fetchColumn();
+
             case PDO::FETCH_ASSOC:
                 return sasql_fetch_assoc($this->result);
             case PDO::FETCH_BOTH:

lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php

@@ -315,6 +315,10 @@ class SQLSrvStatement implements IteratorAggregate, Statement
         $args      = func_get_args();
         $fetchMode = $fetchMode ?: $this->defaultFetchMode;
 
+        if ($fetchMode === PDO::FETCH_COLUMN) {
+            return $this->fetchColumn();
+        }
+
         if (isset(self::$fetchMap[$fetchMode])) {
             return sqlsrv_fetch_array($this->stmt, self::$fetchMap[$fetchMode]) ?: false;
         }

tests/Doctrine/Tests/DBAL/Functional/StatementTest.php

@@ -282,4 +282,13 @@ EOF
             ),
         );
     }
+
+    public function testFetchInColumnMode() : void
+    {
+        $platform = $this->_conn->getDatabasePlatform();
+        $query    = $platform->getDummySelectSQL();
+        $result   = $this->_conn->executeQuery($query)->fetch(\PDO::FETCH_COLUMN);
+
+        self::assertEquals(1, $result);
+    }
 }