Question

Here is the string :'(a+b)+(x/y)*1000′
from that string i want to get ‘(x/y)’ meaning i want the part that contains the division to check later if denominator <> 0 to avoid division by zero.

The string formula can vary but divisions are always between parenthesis.

How can i achieve that in sql ?

Answer 1

Bits that it appears you already have (based on a comment you made)…

• Pos of the '/' = CHARINDEX('/', yourString)
• Pos of the ')' = CHARINDEX(')', yourString, CHARINDEX('/', yourString) + 1)

The position of the ( is a little different, as you need to search backwards. So you need to reverse the string. And so you also need to change the starting position.

• CHARINDEX('(', REVERSE(yourString), LEN(yourString) - CHARINDEX('/', yourString) + 2)

Which give the position from the right hand side. LEN(yourString) - position + 1 give the position from the left hand side.

Add that all together and you get a very long formula…

SUBSTRING(
  yourString,
    LEN(yourString)
  - CHARINDEX('(', REVERSE(yourString), LEN(yourString) - CHARINDEX('/', yourString) + 2)
  + 1,
    CHARINDEX(')', yourString, CHARINDEX('/', yourString) + 1)
  - LEN(yourString)
  + CHARINDEX('(', REVERSE(yourString), LEN(yourString) - CHARINDEX('/', yourString) + 2)
  - 1
)