mysql操作遇到的坑（第二版）

1、通过条件查询出上一条与下一条

sql说明：本表关联本表，然后通过其中一个表，查询出对应的条件，再用另外一个表求出上一条与下一条的数据，求出来的数据是多条的

SELECT

ua.id,

ua.wx_pages,

ua.wx_pages_source,

uaa.id as uaa_id,

uaa.wx_pages,

uaa.wx_pages_source

FROM

ds_user_action AS ua

JOIN ds_user_action AS uaa ON ua.user_id = uaa.user_id // 用会员ID作为关联条件，两张表出来的数据是不同的，其中一张表，专门根据条件用来查询，另外一个没有加条件的表，则用来求上一条与一条数据，切记，不要用主键ID

WHERE

uaa.wx_pages LIKE '%shopping/checkout%'

AND uaa.wx_pages_source LIKE '%goods/goods%'

AND uaa.user_id = 179135

AND ua.id = (

SELECT

max(id)

FROM

ds_user_action as uaaa

WHERE

uaaa.id < uaa.id

AND uaaa.user_id = 179135

)

2、CASE WHEN 判断条件 THEN 值 ELSE 被动值 END 的结果，判断条件排序

（1）ELSE用NULL,count(NULL) == 0 , count(0) == 1

SELECT

　　ld.*, ldt.order_state,

　　ldt.uid,

　　count(

　　CASE

　　WHEN (ldt.order_state = 1) && (ldt.uid = 179135) THEN

　　1

　　ELSE

　　NULL

　　END

) AS onum

FROM

ds_lucky_draw AS ld

LEFT JOIN ds_lucky_deposit AS ldt ON ld.ld_id = ldt.lid

WHERE

ld.`status` = 1

AND ld.lottery_time >= 1564109614

GROUP BY

ld.ld_id

ORDER BY

onum DESC,

ld.lottery_time DESC

（2）这个直接就用的case判断

SELECT

　　ld.*, ldt.order_state,

　　g.goods_name,

　　ldt.uid,

　　CASE

　　WHEN (ldt.order_state = 1) && (ldt.uid = '.$user_id.') THEN

　　1

　　WHEN ld.start_time <= 1564625127 && ld.lottery_time > 1564625127 THEN

　　2

　　WHEN ld.start_time >= 1564625127 THEN

　　3

　　ELSE

　　0

END onum

FROM

ds_lucky_draw AS ld

LEFT JOIN ds_lucky_deposit AS ldt ON ld.ld_id = ldt.lid

LEFT JOIN ds_goods AS g ON ld.goods_id = g.goods_id

WHERE

ld.`status` = 1

AND ld.lottery_time >= 1564625127

GROUP BY

ld.ld_id

ORDER BY

onum DESC,

ld.sort DESC;

3、求出max与本条纪录字段

SELECT

　　lba_id,

　　price,

　　add_time

FROM

ds_live_broadcast_auction AS lba_a

WHERE

lba_a.price = (

　　SELECT

　　　　max(price)

　　FROM

　　ds_live_broadcast_auction AS lba_b

ORDER BY add_time asc

)

limit 1; # 如果价格有多条相同的情况

后续还会更新，谢谢各们亲关注！