MariaDB 10.5

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SELECT (1,2) <=> (1,NULL)

(1,2) <=> (1,NULL)

0

SELECT ((1,2),1) <=> ((1,CAST(NULL AS INT)),1)

((1,2),1) <=> ((1,CAST(NULL AS INT)),1)

0

SELECT ((1,2),1) <=> ((1,NULL),1)

((1,2),1) <=> ((1,NULL),1)

0

SELECT ((1,2),CAST(NULL AS INT)) <=> ((1,CAST(NULL AS INT)),1)

((1,2),CAST(NULL AS INT)) <=> ((1,CAST(NULL AS INT)),1)

0

SELECT ((1,2),null) <=> ((1,null),1)

((1,2),null) <=> ((1,null),1)

0