20220728 sorting strings that are not pure numbers

Meet a need , You need to sort the displacement segments , These displacement sections are like this
Yes 2-2.5L、2.5-3L,3-5L…17L、13L such
The idea is , Take the first number of the string , To sort , If there is “-” Words , Then take “-” The numbers in front , without , Just take “L” Number before .
Need to use sql There are two formulas

SUBSTR( character string , Starting position , End position )-- Split string 
INSTR( character string ,' A symbol ')-- Find the position of a symbol in the string 

there SUBSTR The two split positions of both include this position , such as

SUBSTR('HELLO',0,3)-- have to 'HEL'

therefore , The code is

CASE WHEN INSTR(DISPLACEMENT_SEC,'-')>0 
      THEN SUBSTR(T.DISPLACEMENT_SEC,0,INSTR(DISPLACEMENT_SEC,'-')-1) 
      ELSE SUBSTR(T.DISPLACEMENT_SEC,0,INSTR(DISPLACEMENT_SEC,'L')-1) END AS DIS_SORT

Finally get DIS_SORT Use TO_NUMBER Just put it in order .