MariaDB starting with 10.1.2
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The ST_IsRing function was introduced in MariaDB 10.1.2

Syntax
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ST_IsRing(g)
IsRing(g)

Description
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Returns true if a given LINESTRING is a ring, that is, both ST_IsClosed and
ST_IsSimple. A simple curve does not pass through the same point more than
once. However, see MDEV-7510.

St_IsRing() and IsRing() are synonyms.

URL: https://mariadb.com/kb/en/st_isring/