--Create
CREATE TABLE tests(MC VARCHAR(20),A VARCHAR(20),B VARCHAR(20),LHBH VARCHAR(20),LX INT )
--insert
INSERT INTO tests
SELECT '仓库A<->仓库C','003','004','003004','1'
UNION ALL
SELECT '仓库B<->仓库C','001','004','001004','1'
UNION ALL
SELECT '仓库C<->仓库A','004','003','004003','2'
UNION ALL
SELECT '仓库C<->仓库B','004','001','004001','2'
UNION ALL
SELECT '仓库A<->仓库B','003','001','003001','2'
--select
SELECT * FROM tests
--Query
WITH t AS 
(SELECT t1.*,ROW_NUMBER() OVER (PARTITION BY t1.LX ORDER BY t1.LX) AS BH FROM tests t1
LEFT JOIN tests t2 ON t1.a=t2.b AND t1.b=t2.a
WHERE t2.a IS NOT NULL)
SELECT * FROM t WHERE bh =1
--drop
DROP TABLE tests

MC                   A                    B                    LHBH                 LX          BH
-------------------- -------------------- -------------------- -------------------- ----------- --------------------
仓库A<->仓库C            003                  004                  003004               1           1
仓库C<->仓库A            004                  003                  004003               2           1