这个SQL语句是什么意思？

Question

select count(*) 
from dds#workflow.v_flw_common 
where (instr(substr(performer,0,instr(performer,'@')-1),'%1')>0  
or instr(substr(performer,0,instr(performer,'@')-1),'%1')=1)   
and process_id='%2'特别是这两句
(instr(substr(performer,0,instr(performer,'@')-1),'%1')>0  
or instr(substr(performer,0,instr(performer,'@')-1),'%1')=1) 
我搞了很久都不知到什么意思

Answer 1

instr(
      substr(
              performer,
              0,
              instr(
                   performer,
                   '@'
              )-1
             )
      ,'%1'
) > 0 
只有instr,substr这两个函数
从内向外看

Answer 2

instr(substr(performer,0,instr(performer,'@')-1),'%1')>0  查找字符串performer中＠以前的字各个地方是否含有字符　'%1'

Answer 3

(instr(substr(performer,0,instr(performer,'@')-1),'%1')>0  
or instr(substr(performer,0,instr(performer,'@')-1),'%1')=1) 
-----------------------------------------------------------
Instr(C1,C2,I,J):
在一个字符串中搜索指定的字符,返回发现指定的字符的位置;
C1    被搜索的字符串
C2    希望搜索的字符串
I     搜索的开始位置,默认为1
J     出现的位置,默认为1
-----------------------------------------------------------
SUBSTR(string,start,count):
取子字符串,从start开始,取count个
-----------------------------------------------------------
instr(performer,'@')-1
查找performer中第一个出现＠的位置;减一是因为substr是写的从0开始
-----------------------------------------------------------
substr(performer,0,instr(performer,'@')-1)
截取@以前的字符
-----------------------------------------------------------
instr(substr(performer,0,instr(performer,'@')-1),'%1'
查找截取的字符中是否含有字符'%1'

Answer 4

(instr(substr(performer,0,instr(performer,'@')-1),'%1')>0  
这句诗：截取performer中0到‘@’前一个位置的内容，然后检查是否以‘1’结束。