I am checking to see if an underscore (`_`) is present in a given string or not. If it is found, I want to split the word into two values (a value present before underscore and a value present after underscore).

```
DECLARE @ExpressionToSearch VARCHAR(50) 
    SET @ExpressionToSearch = 'TMS_Customers'
    IF  CHARINDEX('_', @ExpressionToSearch ) > 0 
        PRINT 'Yes it Contains'
    ELSE
        PRINT 'It doesn''t Contain'

Required output
---------------
a=TMS
b=Customers

```

how can i split the given string?