In SQL Server, the PATINDEX function returns the position of the first occurrence of the pattern in the string. Depending on the database collation, the pattern search can be case-insensitive.
In Oracle, you can use the REGEXP_INSTR function but note that the order of parameters and the pattern syntax are different.
SQL Server:
-- Get the position of a letter SELECT PATINDEX('%[a-z]%', '12a45'); # 3 -- Also finds capital 'A' SELECT PATINDEX('%[a-z]%', '12A45'); # 3
Oracle:
-- Get the position of a letter (pattern and order of parameters are changed) SELECT REGEXP_INSTR('12a45', '[a-z]') FROM dual; # 3 -- Does not work for capital 'A' SELECT REGEXP_INSTR('12A45', '[a-z]') FROM dual; # 0
For more information, see SQL Server to Oracle Migration.