Question

我有这样的查询

SELECT DISTINCT Id, AppStatusId,
IF ( (AppStatusId = 80),"1","2" ) as res 
#(here i need res as "1" if AppStatusId = 80 for first 100 rows  )
FROM App
WHERE
AppStatusId = 80
or 
AppTypeId = 100

查询返回1000行，我想将条件为AppStatusId = 80的前100行的res列为1.我期待以下结果

Id, AppStatusId,res
14343  ,80 ,    ,1
2234   ,80 ,    ,1
3232   ,80 ,    ,1
..................
..................
..................
..................
8975,  80,      ,1 # 100th row
3232,  80,      ,0
102,   80,      ,0
103,   80,      ,0
..................
..................
222,   55,      ,0 ( becuase of  or AppTypeId = 100 in where condition)

Answer 1

SELECT
    Id
    ,AppStatusId
    ,if(AppStatusId = 80 AND RowNumber <= 100, 1, 0) as res
FROM
    (
       SELECT
          *
          ,(@rn:= if(AppStatusId = 80, @rn + 1,@rn)) as RowNumber
       FROM
          App a
          CROSS JOIN (SELECT @rn:=0) var
       WHERE
          a.AppStatusId = 80
          OR a.AppTypeId = 100
       ORDER BY
          Id, AppstatusId...., whatever you want for the first 100 records
    ) t

这应该会让你到那里。它会生成一个行号，只有当AppStatusId = 80加上它才会允许您选择记录的任何顺序，这样前100条记录中AppStatusId = 80不必连续，如果你不这样做的话希望他们成为。如果您只是这样订购，它仍然有效。

如何获得第一个＆＃34; n＆＃34;特定条件的行数？

1 个答案: