【批量更新】mysql一个批量更新的例子

##查询
SELECT 
  tcdi.`id` AS contractId,
  tcdp.`id` AS enginId,
  tcdp.`engineering_name` AS engidName,
  tai.`attachment_from_type` AS attFromType,
  tai.`attachment_from_id` AS enginId2,
  '2' AS toAttFromType,
  tcdi.`id` AS toAttfromId
FROM
  `demand_info` tcdi 
  LEFT JOIN demand_pro tcdp 
    ON tcdi.`id` = tcdp.`contract_demand_id` 
  LEFT JOIN attachment_info tai 
    ON tai.`attachment_from_id` = tcdp.`id` 
WHERE tai.`attachment_from_type` = 3
AND tcdi.`id`=3965;

#批量更新
UPDATE 
  attachment_info tai,
  `demand_info` tcdi,
  demand_pro tcdp 
SET
  tai.attachment_from_type = 2,
  tai.attachment_from_id = tcdi.`id` 
WHERE tcdi.`id` = tcdp.`contract_demand_id` 
  AND tai.`attachment_from_id` = tcdp.`id` 
  AND tai.`attachment_from_type` = 3 
  AND tcdi.`id` = 3965; 
  
#更新后查询
SELECT 
  tai.* 
FROM
  `demand_info` tcdi 
  INNER JOIN attachment_info tai 
    ON tai.`attachment_from_id` = tcdi.`id` 
WHERE tai.`attachment_from_type` = 2 
AND tcdi.`id` = 3965;