批量修改同一张表

UPDATE
  private_funds_base e,
  (SELECT LEFT(a.bgdz, 2) bgdz ,a.id FROM
    (SELECT LEFT(private_funds_base.bgdz, 2) bgdz,id FROM private_funds_base ) c,
    private_funds_base a
WHERE 1=1
      ) k
SET
  e.zcs =
  k.bgdz
   WHERE e.id=k.id