diff --git a/lib/Db/AbstractDriver.php b/lib/Db/AbstractDriver.php
index 2a6a973e..66e65f27 100644
--- a/lib/Db/AbstractDriver.php
+++ b/lib/Db/AbstractDriver.php
@@ -204,4 +204,8 @@ abstract class AbstractDriver implements Driver {
     public function prepare(string $query, ...$paramType): Statement {
         return $this->prepareArray($query, $paramType);
     }
+
+    public function stringOutput(): bool {
+        return false;
+    }
 }
diff --git a/lib/Db/Driver.php b/lib/Db/Driver.php
index 09f16e78..6f1e311f 100644
--- a/lib/Db/Driver.php
+++ b/lib/Db/Driver.php
@@ -72,6 +72,7 @@ interface Driver {
      * The tokens the implementation must understand are:
      *
      * - "greatest": the GREATEST function implemented by PostgreSQL and MySQL
+     * - "least": the LEAST function implemented by PostgreSQL and MySQL
      * - "nocase": the name of a general-purpose case-insensitive collation sequence
      * - "like": the case-insensitive LIKE operator
      * - "integer": the integer type to use for explicit casts
@@ -91,4 +92,7 @@ interface Driver {
      * This should be restricted to quick maintenance; in SQLite terms it might include ANALYZE, but not VACUUM
      */
     public function maintenance(): bool;
+
+    /** Reports whether the implementation will coerce integer and float values to text (string) */
+    public function stringOutput(): bool;
 }
diff --git a/lib/Db/MySQL/Driver.php b/lib/Db/MySQL/Driver.php
index 10bc766d..fa7a9752 100644
--- a/lib/Db/MySQL/Driver.php
+++ b/lib/Db/MySQL/Driver.php
@@ -12,7 +12,7 @@ use JKingWeb\Arsse\Db\Exception;
 class Driver extends \JKingWeb\Arsse\Db\AbstractDriver {
     use ExceptionBuilder;
 
-    protected const SQL_MODE = "ANSI_QUOTES,HIGH_NOT_PRECEDENCE,NO_BACKSLASH_ESCAPES,NO_ENGINE_SUBSTITUTION,PIPES_AS_CONCAT,STRICT_ALL_TABLES";
+    protected const SQL_MODE = "ANSI_QUOTES,HIGH_NOT_PRECEDENCE,NO_BACKSLASH_ESCAPES,NO_ENGINE_SUBSTITUTION,PIPES_AS_CONCAT,STRICT_ALL_TABLES,NO_UNSIGNED_SUBTRACTION";
     protected const TRANSACTIONAL_LOCKS = false;
 
     /** @var \mysqli */
diff --git a/lib/Db/MySQL/PDODriver.php b/lib/Db/MySQL/PDODriver.php
index 18cda0be..590b73c4 100644
--- a/lib/Db/MySQL/PDODriver.php
+++ b/lib/Db/MySQL/PDODriver.php
@@ -29,7 +29,7 @@ class PDODriver extends Driver {
         try {
             $this->db = new \PDO($dsn, $user, $password, [
                 \PDO::ATTR_ERRMODE           => \PDO::ERRMODE_EXCEPTION,
-                \PDO::ATTR_STRINGIFY_FETCHES => true,
+                \PDO::ATTR_STRINGIFY_FETCHES => false,
             ]);
         } catch (\PDOException $e) {
             $msg = $e->getMessage();
diff --git a/lib/Db/PostgreSQL/Driver.php b/lib/Db/PostgreSQL/Driver.php
index f78855cf..e290967a 100644
--- a/lib/Db/PostgreSQL/Driver.php
+++ b/lib/Db/PostgreSQL/Driver.php
@@ -232,4 +232,8 @@ class Driver extends \JKingWeb\Arsse\Db\AbstractDriver {
         $this->exec("ANALYZE");
         return true;
     }
+
+    public function stringOutput(): bool {
+        return true;
+    }
 }
diff --git a/lib/Db/PostgreSQL/PDODriver.php b/lib/Db/PostgreSQL/PDODriver.php
index 93daf667..71d18eb9 100644
--- a/lib/Db/PostgreSQL/PDODriver.php
+++ b/lib/Db/PostgreSQL/PDODriver.php
@@ -60,4 +60,8 @@ class PDODriver extends Driver {
     public function prepareArray(string $query, array $paramTypes): \JKingWeb\Arsse\Db\Statement {
         return new PDOStatement($this->db, $query, $paramTypes);
     }
+
+    public function stringOutput(): bool {
+        return false;
+    }
 }
diff --git a/lib/Db/SQLite3/PDODriver.php b/lib/Db/SQLite3/PDODriver.php
index 86ab1cdc..87ecfc30 100644
--- a/lib/Db/SQLite3/PDODriver.php
+++ b/lib/Db/SQLite3/PDODriver.php
@@ -81,4 +81,8 @@ class PDODriver extends AbstractPDODriver {
             }
         }
     }
+
+    public function stringOutput(): bool {
+        return true;
+    }
 }
diff --git a/tests/lib/AbstractTest.php b/tests/lib/AbstractTest.php
index a22913df..f498a543 100644
--- a/tests/lib/AbstractTest.php
+++ b/tests/lib/AbstractTest.php
@@ -422,7 +422,7 @@ abstract class AbstractTest extends \PHPUnit\Framework\TestCase {
                     // serialize to CSV, null being represented by no value
                     if ($v === null) {
                         $row[] = "";
-                    } elseif (static::$stringOutput || is_string($v)) {
+                    } elseif ($drv->stringOutput() || is_string($v)) {
                         $row[] = '"'.str_replace('"', '""', (string) $v).'"';
                     } else {
                         $row[] = (string) $v;
diff --git a/tests/lib/DatabaseDrivers/MySQLPDO.php b/tests/lib/DatabaseDrivers/MySQLPDO.php
index 46248684..ba01dd4e 100644
--- a/tests/lib/DatabaseDrivers/MySQLPDO.php
+++ b/tests/lib/DatabaseDrivers/MySQLPDO.php
@@ -16,7 +16,7 @@ trait MySQLPDO {
     protected static $dbResultClass = \JKingWeb\Arsse\Db\PDOResult::class;
     protected static $dbStatementClass = \JKingWeb\Arsse\Db\MySQL\PDOStatement::class;
     protected static $dbDriverClass = \JKingWeb\Arsse\Db\MySQL\PDODriver::class;
-    protected static $stringOutput = true;
+    protected static $stringOutput = false;
 
     public static function dbInterface() {
         try {
@@ -33,7 +33,7 @@ trait MySQLPDO {
             $dsn = "mysql:".implode(";", $dsn);
             $d = new \PDO($dsn, Arsse::$conf->dbMySQLUser, Arsse::$conf->dbMySQLPass, [
                 \PDO::ATTR_ERRMODE                => \PDO::ERRMODE_EXCEPTION,
-                \PDO::ATTR_STRINGIFY_FETCHES      => true,
+                \PDO::ATTR_STRINGIFY_FETCHES      => false,
                 \PDO::MYSQL_ATTR_MULTI_STATEMENTS => false,
             ]);
             foreach (\JKingWeb\Arsse\Db\MySQL\PDODriver::makeSetupQueries() as $q) {