Oracle 18c

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with tbl as
(
    select
        XMLType(
        '<singleAggregatePaymentResponse xmlns:ns7="http://www.mtszn.kz/services/PersonCotracts/schemas">
			<ns7:isEspPayer xmlns="http://www.mtszn.kz/services/PersonCotracts/schemas">true</ns7:isEspPayer>
			<ns7:periods xmlns="http://www.mtszn.kz/services/PersonCotracts/schemas">
				<period>122019</period>
				<period>112019</period>
				<period>102019</period>
				<period>092019</period>
				<period>082019</period>
				<period>072019</period>
				<period>062019</period>
				<period>052019</period>
				<period>042019</period>
				<period>032019</period>
				<period>022019</period>
				<period>012019</period>
			</ns7:periods>
		</singleAggregatePaymentResponse>'
        ) xmldata
    from
        dual
)
select period
from   tbl,
       xmltable(
			xmlnamespaces('http://www.mtszn.kz/services/PersonCotracts/schemas' as "ns1"),
			'/singleAggregatePaymentResponse/ns1:periods/ns1:period'
                      PASSING tbl.xmldata 
                      COLUMNS period VARCHAR2(10) PATH '.');

PERIOD
122019
112019
102019
092019
082019
072019
062019
052019
042019
032019
022019
012019