mapper:

IPage<PurchasePlan> listWithZj(Page page, @Param(Constants.WRAPPER) Wrapper<PurchasePlan> wrapper);

xml:

 <select id="listWithZj" resultType="org.jeecg.modules.gz.purchase.entity.PurchasePlan">
        select a.*,case when b.project_id is null then 0 else 1 end hasLz from gz_purchase_plan a
        left join projectlz b
        on a.id=b.plan_id
        ${ew.customSqlSegment}
    </select>