SQL 获取字符串和特殊字符之间的字符

Question

I am trying to convert the format of work weeks. The current format looks like this:

workweek
------------
2020ww20.5
2020ww18.3
2019ww05.2

I want to convert format to:

workweek
------------
202020
202018
202005

Here is what I have tried:

SUBSTRING(workweek,
    CHARINDEX('ww',workweek)+2,
    CHARINDEX('.',workweek)- CHARINDEX('ww',workweek)-1)

workweek outcome: 202020.

I've also tried

SUBSTRING(workweek,
    PATINDEX('%ww%', workweek)+1,
    PATINDEX('%.%', workweek) - PATINDEX('%ww%', workweek))

workweek outcome: 2020w20

Thank you in advance

Answer 1

If your strings always follow this fixed format, then substring() is just enough:

concat(
    substring(workweek, 1, 4),
    substring(workweek, 7, 2)
)

Demo on DB Fiddle :

select workweek, concat(substring(workweek, 1, 4), substring(workweek, 7, 2)) result
from (values ('2020ww20.5'), ('2020ww18.3'), ('2019ww05.2')) as t(workweek);

workweek   | result
:--------- | :-----
2020ww20.5 | 202020
2020ww18.3 | 202018
2019ww05.2 | 201905

Answer 2

You could replace "ww" and get everything left to the 6th character

  left(replace(workweek,'ww',''),6)