一個sql查詢語句(記錄學習的點滴)

查詢選擇時間的前一天的最大時間的記錄信息？
原sql語句：
方法一：
SELECT b.BDHSL FROM w_pckcbd b WHERE a.pc_id = b.pc_id
AND b.AAE036 = (
SELECT c.AAE036 FROM w_pckcbd c
WHERE c.AAE036 < '2017-05-09 00:00:00'  ORDER BY  c.AAE036 DESC LIMIT 0,1
)
方法二：
SELECT b.BDHSL FROM w_pckcbd b WHERE a.pc_id = b.pc_id
AND b.AAE036 = (
SELECT MAX(c.AAE036) FROM w_pckcbd c
WHERE c.AAE036 < '2017-05-09 00:00:00'
)

改進sql語句：
SELECT b.BDHSL FROM w_pckcbd b WHERE a.pc_id = b.pc_id
AND b.aae036 < '2017-05-09 00:00:00' ORDER BY b.AAE036 DESC LIMIT 0,1