What is charindex and patindex? how it is useful in single row functions?

Question

I am learning sql for past two weeks. I didn't find any proper and clear answer for the above question. anyone who knows a proper version of answer can share

Answer 1

The CHARINDEX and PATINDEX functions return the starting position of a pattern you specify. PATINDEX can use wildcard characters, but CHARINDEX cannot. ... With CHARINDEX, the pattern is a literal string without wildcard characters. A string-valued expression, generally a column name, searched for the specified pattern.