Question

我有一个像这样的tabe：

sn(char)   ts(int)     data(char) flag(tinyint)
'a'        1494825611  'a0'       1
'a'        1494825613  'a1'       0
'a'        1494825617  'a2'       0
'a'        1494825623  'a3'       1
'a'        1494825634  'a4'       1
'b'        1494825644  'b1'       1
'b'        1494825643  'b0'       0
'a'        1494825645  'a5'       1
'a'        1494825648  'a6'       0
'b'        1494825658  'b2'       1

行的顺序可能不正确（例如b1和b0），因此首先应按ts排序。

我正在尝试对sn进行有效查询，以获取当前和下一个flag不同的行。

因此，对sn 'a'：

我需要这样的内容

old_ts     ts         old_data data flag
1494825611 1494825613 'a0'     'a1' 0
1494825617 1494825623 'a2'     'a3' 1
1494825645 1494825648 'a5'     'a6' 0

和sn 'b'：

old_ts     ts         old_data data flag
1494825643 1494825644 'b0',    'b1' 1

创建其他列或表不是问题。

Answer 1

您可以使用@rowFlag变量。每行检查它是否等于标志。如果是，则将过滤器字段设置为0以稍后跳过

select old_ts, ts, old_data, data, new_flag as flag
from
    (select
      t.ts,
      t.data,
      case when @rowFlag=flag then 0 else 1 end as filter,
      flag as new_flag,
      @rowFlag:=flag as old_flag,
      @old as old_data,
      @old:=data,
      @old_ts as old_ts,
      @old_ts:=ts
    from  test t, (select @rowFlag:=-1, @old:=null, @old_ts:=null) as def
    where sn='a'
    order by ts) as sub
where filter=1 and old_ts is not null;

SQL Fiddle

Answer 2

您可以检查此内容，因为它还包含旧值和新值。使用您的实际表名更改new_table。

select a.sn, a.ts as oldts, b.ts as newts, 
a.data as old_data, b.data as data, a.flag  as old_flag , b.flag as flag
from (
select sn, ts, data, flag , 
if(@oldSn = sn,@rowNumber := @rowNumber + 1,@rowNumber := 1) as row_number, 
@oldSn := sn as curentsn
from new_table
order by sn, ts ) a 
join  (
select sn, ts, data, flag , 
if(@oldSn1 = sn,@rowNumber := @rowNumber + 1,@rowNumber := 1) as row_number, 
@oldSn1 := sn as curentsn
from new_table
order by sn, ts ) b  on  a.sn = b.sn 
and a.row_number + 1 = b.row_number
where a.flag != b.flag

以上查询的输出

sn, oldts, newts, old_data, data, old_flag, flag
a, 1494825611, 1494825613, a0, a1, 1, 0
a, 1494825617, 1494825623, a2, a3, 0, 1
a, 1494825645, 1494825648, a5, a6, 1, 0
b, 1494825643, 1494825644, b0, b1, 0, 1

MySQL SELECT跟随具有不同列值的行

2 个答案: