在case语句中缺少表达式错误

Question

我有源表Test包含id列，目标表testm由id , col2组成。请帮助我摆脱这个错误。

test (source)     

id        
---        
10      
10 
20 
20 
20 
30 
30 
40 

目标

testm 

id col2     
-- ----     
10 1     
10 2   
20 1   
20 2   
20 3   
30 1   
30 2   
40 1   

查询：

select id, (case id 
      when 10 then select count(id) from test where id =10 
      when 20 then select count(id) from test where id =20 
      when 30 then select count(id) from test where id =30 
      when 40 then select count(id) from test where id =40 
else 0 END) col2 from test 

引发错误：

missing expression

Answer 1

通过观察所需的输出我想这要编号的每个g的出现roups;如果这是使用ROW_NUMBER解析函数应该做你想要什么情况：

select id, row_number() over (partition by id order by id) as col2 
from test 
order by id; 

见这个样本SQL Fiddle

给你示例源数据，这将是输出：

| ID | COL2 | 
|----|------| 
| 10 | 1 | 
| 10 | 2 | 
| 20 | 1 | 
| 20 | 2 | 
| 20 | 3 | 
| 30 | 1 | 
| 30 | 2 | 
| 40 | 1 |