The expression can be a string or a complex expression containing operators. Treats the expression within the parentheses as a unit. The expression a|b matches the character a or b. The expression x matches the string jx, but does not match ax, fx, or ix. The expression def matches the string xdef, but not adef, bdef, or cdef. Matches any single character not in the list within the brackets.įor information about operators and ranges in the character list, see the description of the Matching Character List operator. The expression matches the first character in the strings all, bill, and cold, but does not match any characters in doll. In Oracle Database, the linguistic range is determined by the NLS_SORT initialization parameter. Thus, ranges are linguistic rather than byte value ranges the semantics of the range expression are independent of the character set. Note: In the POSIX standard, a range includes all collation elements between the start and end of the range in the linguistic definition of the current locale. A right bracket ( ]) is treated as a literal if it occurs first in the list. In the list, all operators except these are treated as literals:Ī dash ( -) is a literal when it occurs first or last in the list, or as an ending range point in a range expression, as in. Matches any single character in the list within the brackets. matches the strings aaa, aaaa, and aaaaa, but does not match aa or aaaaaa. Previously, finding a match for a protein sequence such as. Oracle SQL support for regular expressions lets application developers implement complex pattern-matching logic in the database, which is useful for these reasons:īy centralizing pattern-matching logic in the database, you avoid intensive string processing of SQL results sets by middle-tier applications.įor example, life science customers often rely on PERL to do pattern analysis on bioinformatics data stored in huge databases of DNA and proteins. This robust pattern-matching functionality is one reason that many application developers use PERL. For example, a PERL script can read the contents of each HTML file in a directory into a single string variable and then use a regular expression to search that string for URLs. Regular expressions are a powerful text-processing component of the programming languages Java and PERL. Thus, the preceding regular expression matches these strings: The question mark ( ?) indicates that the preceding element, s, is optional. The pipe symbol ( |) indicates a choice between the elements on either side of it, f and ht. Parentheses group multiple pattern elements into a single element. The character literals are f, ht, tp, s, and the colon ( :). The metacharacters (which are also operators) in the preceding example are the parentheses, the pipe symbol ( |), and the question mark ( ?). For example, this regular expression matches any string that begins with either f or ht, followed by tp, optionally followed by s, followed by the colon ( :): A regular expression specifies a search pattern, using metacharacters (which are, or belong to, operators) and character literals (described in Oracle Database SQL Language Reference).
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