update
    agreement_list_tmp
    USE INDEX (ind_agreement_5fields)
        JOIN
    agreement_list_tmp a ON 
    (a.AgreementNumber = agreement_list_tmp.AgreementNumber
         AND a.AgreementTypeID = agreement_list_tmp.AgreementTypeID
         AND a.CustomerSiteID = agreement_list_tmp.CustomerSiteID
         AND a.Source = agreement_list_tmp.Source
	)

set agreement_list_tmp.ActualEndDate = agreement_list_tmp.EndDate
WHERE a.ParentAgreementNumber > 0
;

CREATE INDEX ind_agreement_5fields ON agreement (`AgreementNumber`,`AgreementTypeID`,`CustomerSiteID`,`Source`);

1	SIMPLE	a	range	AgreementTypeID,CustomerSiteID,index5,ParentAgreementNumber,index2017060601,agreement_AgreementNumber,ind_agreement,ind_agreement_test,ind_agreement_5fields,ind_agreement_full	ParentAgreementNumber	4	NULL	1997	Using where
1	SIMPLE	agreement_list_tmp	ref	ind_agreement_5fields	ind_agreement_5fields	12	sedbqa.a.AgreementNumber,sedbqa.a.AgreementTypeID,sedbqa.a.CustomerSiteID	1	Using where