postgressql 按符号切割字符串 从单列到多列
 split_part(channel, '/', 1) AS channel1 
              , split_part(channel, '/', 2) AS channel2
							, split_part(channel, '/', 3) AS channnel3
  
分完之后的结果 是这个样子
 split_part(channel, '/', 1) AS channel1 
              , split_part(channel, '/', 2) AS channel2
							, split_part(channel, '/', 3) AS channnel3
  
分完之后的结果 是这个样子
