ydb/yql/essentials/tests/s-expressions/suites/MultiIO/MuxOverRead.yql

(
(let mr_source (DataSource 'yt 'plato))
(let mr_sink (DataSink 'yt 'plato))

(let x (Read! world mr_source (Key '('table (String 'Input1))) (Void) '()))
(let world (Left! x))
(let data1 (Right! x))

(let x (Read! world mr_source (Key '('table (String 'Input2))) (Void) '()))
(let world (Left! x))
(let data2 (Right! x))

(let data (Mux '(data1 data2)))

(let data (Map data (lambda '(item) (block '(
    (let res (Visit item
        '0 (lambda '(x) x)
        '1 (lambda '(x) x)
    ))
   (return res)
)))))

(let world (Write! world mr_sink (Key '('table (String 'Output1))) data '('('mode 'renew))))

(let world (Commit! world mr_sink))
(return world)
)