sql 鏈表查詢語句

SELECT
    *
FROM
    jcb_t_asset_combo_item AS jtaci
**INNER join** (select pType,pId,(**CASE WHEN ISNULL(pTrustId)** THEN pFundId ELSE pTrustId END) AS choiceId FROM jcb_t_product) AS product ON product.pId = jtaci.itemRelatedProduct
//連接一個查詢出結果的表，該查詢出來的結果表有三個字段。type，id，choiceId、
其中Choiceid是通過case When 語句進行判斷的。得出來的choiceId 在和下面的新生成的表進行連接
INNER JOIN (
    select product_name as pname ,product_id AS detailId ,product_period AS pqixian, product_rate AS pshouyi ,1 as type from jcb_tnonstandardproduct
 union 
select pFundName as pname ,pFundId AS detailId ,dataDate AS pqoxian ,tenThousandBenifitRate AS pshouyi,2 as type from jcb_t_standerproduct_fund
 ) AS detail **ON detail.detailId = product.choiceId** and detail.type=product.pType
//此連接的表也是新生成的，通過union關鍵字，進行兩個不同的類型的字段進行聯合。同時與上一個表的choiceId進行對接
WHERE
    jtaci.itemRelatedAssetPack = 2