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# EXPORT and IMPORT
A mechanism for putting part of the query into a separate attached file. To use the mechanism, you need to set the following pragma in the query:
* [PRAGMA Library](pragma.md#library) — marks the attached file as available for import.
## EXPORT
`EXPORT $my_symbol1, $my_symbol2, ...;` lists the names of named expressions in the library that are available for import.
## IMPORT
`IMPORT my_library SYMBOLS $my_symbol1, $my_symbol2, ...;` makes the listed named expressions available for further use.
{% note info %}
[Lambdas](expressions.md#lambda), [actions](action.md), [named subqueries](subquery.md), constant values, and expressions can be transferred to the library, but __subqueries or aggregate functions__ cannot be.
{% endnote %}
{% note warning %}
The file linked by the [PRAGMA Library](pragma.md#library) must be attached to the query. __You can't use [PRAGMA File](pragma.md#file) for this purpose__.
{% endnote %}
## Example
my_lib.sql:
```yql
$Square = ($x) -> { RETURN $x * $x; };
$Sqrt = ($x) -> { RETURN Math::Sqrt($x); };
-- Aggregation functions created using
-- AggregationFactory, convenient to transfer to the library
$Agg_sum = AggregationFactory("SUM");
$Agg_max = AggregationFactory("MAX");
EXPORT $Square, $Sqrt, $Agg_sum, $Agg_max;
```
Query:
```yql
PRAGMA Library("my_lib.sql");
IMPORT my_lib SYMBOLS $Square, $Sqrt, $Agg_sum, $Agg_max;
SELECT
$Square(2), -- 4
$Sqrt(4); -- 2
SELECT
AGGREGATE_BY(x, $Agg_sum), -- 5
AGGREGATE_BY(x, $Agg_max) -- 3
FROM (
SELECT 2 AS x
UNION ALL
SELECT 3 AS x
)
```
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