yii\db\mssql\Schema::findColumns PHP Method

    protected function findColumns($table)
    {
        $columnsTableName = 'INFORMATION_SCHEMA.COLUMNS';
        $whereSql = "[t1].[table_name] = '{$table->name}'";
        if ($table->catalogName !== null) {
            $columnsTableName = "{$table->catalogName}.{$columnsTableName}";
            $whereSql .= " AND [t1].[table_catalog] = '{$table->catalogName}'";
        }
        if ($table->schemaName !== null) {
            $whereSql .= " AND [t1].[table_schema] = '{$table->schemaName}'";
        }
        $columnsTableName = $this->quoteTableName($columnsTableName);
        $sql = <<<SQL
SELECT
    [t1].[column_name], [t1].[is_nullable], [t1].[data_type], [t1].[column_default],
    COLUMNPROPERTY(OBJECT_ID([t1].[table_schema] + '.' + [t1].[table_name]), [t1].[column_name], 'IsIdentity') AS is_identity,
    CONVERT(VARCHAR, [t2].[value]) AS comment
FROM {$columnsTableName} AS [t1]
LEFT OUTER JOIN [sys].[extended_properties] AS [t2] ON
    [t2].[minor_id] = COLUMNPROPERTY(OBJECT_ID([t1].[TABLE_SCHEMA] + '.' + [t1].[TABLE_NAME]), [t1].[COLUMN_NAME], 'ColumnID') AND
    OBJECT_NAME([t2].[major_id]) = [t1].[table_name] AND
    [t2].[class] = 1 AND
    [t2].[class_desc] = 'OBJECT_OR_COLUMN' AND
    [t2].[name] = 'MS_Description'
WHERE {$whereSql}
SQL;
        try {
            $columns = $this->db->createCommand($sql)->queryAll();
            if (empty($columns)) {
                return false;
            }
        } catch (\Exception $e) {
            return false;
        }
        foreach ($columns as $column) {
            $column = $this->loadColumnSchema($column);
            foreach ($table->primaryKey as $primaryKey) {
                if (strcasecmp($column->name, $primaryKey) === 0) {
                    $column->isPrimaryKey = true;
                    break;
                }
            }
            if ($column->isPrimaryKey && $column->autoIncrement) {
                $table->sequenceName = '';
            }
            $table->columns[$column->name] = $column;
        }
        return true;
    }