The case sensitivity or insensitivity depends on the collation applied to the column or at the DB level ..
Normally, the default collation is ‘CI’ but please remember it is not always ‘Case Insensitive’
If you run the below query on any particular db server ..
what you could retrieve the data value, normally would be,
Latin1_General_CI_AS (CI – Case Insensitive, AS – Accent Sensitive)
But it could also be something like this …
So though it may take an additional 1/100th of a nano-second, I'd generally prefer to UPPERize the string comparison such as below …
UPPER(SUBSTRING(COMMENT_,1,8)) = 'Schedule'
instead of exact match such as
SUBSTRING(COMMENT_, 1, 8) = 'Schedule'