MDL-52817 dml: implement driver methods for SQL group concatenation.

2021-02-19 15:31:00 +00:00
parent a93828a188
commit b2d19cc29f
9 changed files with 226 additions and 0 deletions
@@ -1452,6 +1452,19 @@ class pgsql_native_moodle_database extends moodle_database {
        return " $s ";
    }

+    /**
+     * Return SQL for performing group concatenation on given field/expression
+     *
+     * @param string $field
+     * @param string $separator
+     * @param string $sort
+     * @return string
+     */
+    public function sql_group_concat(string $field, string $separator = ', ', string $sort = ''): string {
+        $fieldsort = $sort ? "ORDER BY {$sort}" : '';
+        return "STRING_AGG(CAST({$field} AS VARCHAR), '{$separator}' {$fieldsort})";
+    }
+
    public function sql_regex_supported() {
        return true;
    }