diff --git a/lib/dml/oci_native_moodle_database.php b/lib/dml/oci_native_moodle_database.php
index aa073fb3d67..67099bda2c4 100644
--- a/lib/dml/oci_native_moodle_database.php
+++ b/lib/dml/oci_native_moodle_database.php
@@ -689,15 +689,13 @@ class oci_native_moodle_database extends moodle_database {
         if (is_bool($value)) { // Always, convert boolean to int
             $value = (int)$value;
 
-        } else if ($column->meta_type == 'B') { // BLOB detected, we return 'blob' array instead of raw value to allow
-            if (!is_null($value)) {             // binding/executing code later to know about its nature
-                $value = array('blob' => $value);
-            }
+        } else if ($column->meta_type == 'B' && !is_null($value)) {
+            // Not null BLOB detected, we return 'blob' array instead for later handing on binding.
+            $value = array('blob' => $value);
 
-        } else if ($column->meta_type == 'X' && strlen($value) > 4000) { // CLOB detected (>4000 optimisation), we return 'clob'
-            if (!is_null($value)) {                                      // array instead of raw value to allow binding/
-                $value = array('clob' => (string)$value);                // executing code later to know about its nature
-            }
+        } else if ($column->meta_type == 'X' && !is_null($value) && strlen($value) > 4000) {
+            // Not null CLOB detected (>4000 optimisation), we return 'clob' array instead for later handing on binding.
+            $value = array('clob' => (string)$value);
 
         } else if ($value === '') {
             if ($column->meta_type == 'I' or $column->meta_type == 'F' or $column->meta_type == 'N') {
@@ -962,7 +960,7 @@ class oci_native_moodle_database extends moodle_database {
                     // passed in an arbitrary sql (not processed by normalise_value() ever,
                     // and let's handle it as such. This will provide proper binding of CLOBs in
                     // conditions and other raw SQLs not covered by the above function.
-                    if (strlen($value) > 4000) {
+                    if (!is_null($value) && strlen($value) > 4000) {
                         $lob = oci_new_descriptor($this->oci, OCI_DTYPE_LOB);
                         if ($descriptors === null) {
                             throw new coding_exception('moodle_database::bind_params() $descriptors not specified for clob');
diff --git a/lib/dml/pgsql_native_moodle_database.php b/lib/dml/pgsql_native_moodle_database.php
index 9ab215e4ea1..a61b4f89dec 100644
--- a/lib/dml/pgsql_native_moodle_database.php
+++ b/lib/dml/pgsql_native_moodle_database.php
@@ -545,7 +545,7 @@ class pgsql_native_moodle_database extends moodle_database {
         $tablename = $this->prefix.$table;
 
         $sql = "SELECT a.attnum, a.attname AS field, t.typname AS type, a.attlen, a.atttypmod, a.attnotnull, a.atthasdef,
-                       CASE WHEN a.atthasdef THEN pg_catalog.pg_get_expr(d.adbin, d.adrelid) END AS adsrc
+                       CASE WHEN a.atthasdef THEN pg_catalog.pg_get_expr(d.adbin, d.adrelid) ELSE '' END AS adsrc
                   FROM pg_catalog.pg_class c
                   JOIN pg_catalog.pg_namespace as ns ON ns.oid = c.relnamespace
                   JOIN pg_catalog.pg_attribute a ON a.attrelid = c.oid
diff --git a/lib/xmldb/xmldb_field.php b/lib/xmldb/xmldb_field.php
index 25946b4a80c..12061685cc2 100644
--- a/lib/xmldb/xmldb_field.php
+++ b/lib/xmldb/xmldb_field.php
@@ -116,25 +116,27 @@ class xmldb_field extends xmldb_object {
      */
     public function set_attributes($type, $precision=null, $unsigned=null, $notnull=null, $sequence=null, $default=null, $previous=null) {
         $this->type = $type;
-    /// Try to split the precision into length and decimals and apply
-    /// each one as needed
-        $precisionarr = explode(',', $precision);
-        if (isset($precisionarr[0])) {
-            $this->length = trim($precisionarr[0]);
+
+        // LOBs (BINARY OR TEXT) don't support any precision (neither length or decimals).
+        if ($type == XMLDB_TYPE_BINARY || $this->type == XMLDB_TYPE_TEXT) {
+            $this->length = null;
+            $this->decimals = null;
+
+        } else if (!is_null($precision)) {
+            // Try to split the not null precision into length and decimals and apply each one as needed.
+            $precisionarr = explode(',', $precision);
+            if (isset($precisionarr[0])) {
+                $this->length = trim($precisionarr[0]);
+            }
+            if (isset($precisionarr[1])) {
+                $this->decimals = trim($precisionarr[1]);
+            }
         }
-        if (isset($precisionarr[1])) {
-            $this->decimals = trim($precisionarr[1]);
-        }
-        $this->precision = $type;
+
         $this->notnull = !empty($notnull) ? true : false;
         $this->sequence = !empty($sequence) ? true : false;
         $this->setDefault($default);
 
-        if ($this->type == XMLDB_TYPE_BINARY || $this->type == XMLDB_TYPE_TEXT) {
-            $this->length = null;
-            $this->decimals = null;
-        }
-
         $this->previous = $previous;
     }