SQL，ORCLE，MySQL的

Question

我的表是：

table_nm：问题

q_nm    |     q_txt
----------------------
store   |     abc
store   |     efg
store   |     lmn
store   |     pqr
store   |     noc
buy     |     abab
buy     |     bcbcv
buy     |     drtju
overall |     lili
overall |     mimi

我希望输出如下：

q_nm    |     q_txt
----------------------
store   |     abc
        |     efg
        |     lmn
        |     pqr
        |     noc
buy     |     abab
        |     bcbcv
        |     drtju
overall |     lili
        |     mimi

如何获得以上输出。请帮帮我。

Answer 1

简单!!! 将当前q_nm与前一行的q_nm进行比较。如果它们相等则使其为空，否则为q_nm。 以下是应用上述逻辑的查询。

  Select 
  CASE WHEN (LAG(Q_NM,1) OVER (ORDER BY Q_NM)) LIKE Q_NM
  THEN NULL
  ELSE Q_NM
  END as Q_NM,
  Q_TXT
  from table_name

Answer 2

在Oracle中，您可以通过lag函数执行此操作。

注意：由于没有要排序的列，因此无法保证同一q_txt的{​​{1}}顺序。

q_num

输出：

  with tbl(q_nm,q_txt) as (
  select 'store','abc  ' from dual union all
  select 'store','efg  ' from dual union all
  select 'store','lmn  ' from dual union all
  select 'store','pqr  ' from dual union all
  select 'store','noc  ' from dual union all
  select 'buy','abab ' from dual union all
  select 'buy','bcbcv' from dual union all
  select 'buy','drtju' from dual union all
  select 'overall','lili ' from dual union all
  select 'overall','mimi ' from dual
  )
  select 
    case when q_nm=prev_q_nm 
       then null 
       else q_nm 
  end as q_nm
      ,q_txt
  from 
  (select q_nm,q_txt,lag(q_nm,1,0) over (order by q_nm,q_txt) as prev_q_nm from tbl
  )