Pattern Matching and Regex

Question 1

Start With

Question 2

End with

Answer 2

$

Question 3

Any single character

Answer 3

.

Question 4

Zero or one

Answer 4

?

Question 5

zero or many

Answer 5

*

Question 6

One or many

Answer 6

+

Question 7

OR operator

Answer 7

|

Question 8

[abc]

Answer 8

:set

Question 9

[^abc]

Answer 9

:set not equal

Question 10

[a-f]

Answer 10

:range

Question 11

[^a-f]

Answer 11

:range not equal

Question 12

~

Answer 12

True/False Regex:
Tests the value on the left against the regex on the right and returns true if the regex can match within the value.
Note that the regex does not have to fully match the whole value, it just has to match a part.

text ~ text → boolean
String matches regular expression, case sensitively
‘thomas’ ~ ‘t.*ma’ → t

Question 13

~*

Answer 13

True/False Regex:
Case insensitive version of ~.
Tests the value on the left against the regex on the right and returns true if the regex can match within the value.

text ~* text → boolean
String matches regular expression, case insensitively
‘thomas’ ~* ‘T.*ma’ → t

Question 14

.

Answer 14

Matches any character

Question 15

\s

Answer 15

Matches “empty space” characters like space and tab

Question 16

\S

Answer 16

Matches anything that isn’t a space

Question 17

\d

Answer 17

Matches any digit character

Question 18

\D

Answer 18

Matches any non-digit character

Question 19

\w

Answer 19

Matches any “word” character (a-z, 0-9)

Question 20

\W

Answer 20

Matches any non-word character

Answer 21

Binds the pattern to the start of the input

Question 22

$

Answer 22

Binds the pattern to the end of the input

Question 23

( )

Answer 23

Group items in a single logical item to be made available for further processing.

Example:
c(a|o)%.
Matches: can, corn, cop

Question 24

*

Answer 24

Matches 0-N repetitions of the character preceding it

Question 25

+

Answer 25

Matches 1-N repetitions of the character preceding it

Question 26

{N}

Answer 26

Matches N repetitions of the character preceding it

Question 27

^A+

Answer 27

Would match strings that start with one-or-more ‘A’ characters

Question 28

\d+

Answer 28

Would match any combination of one-or-more digits in order

Question 29

^\S

Answer 29

Would match any string that did not start with white space

Question 30

!~

Answer 30

text !~ text → boolean
String does not match regular expression, case sensitively
‘thomas’ !~ ‘t.*max’ → t

Question 31

!~*

Answer 31

text !~* text → boolean
String does not match regular expression, case insensitively
‘thomas’ !~* ‘T.*ma’ → f

Question 32

regex_replace()

Answer 32

Provides substitution of new text for substrings that match POSIX regular expression patterns. It has the syntax regexp_replace(source, pattern, replacement [, flags ]).

The source string is returned unchanged if there is no match to the pattern. If there is a match, the source string is returned with the replacement string substituted for the matching substring.

Examples:
regexp_replace(‘foobarbaz’, ‘b..’, ‘X’)
fooXbaz
regexp_replace(‘foobarbaz’, ‘b..’, ‘X’, ‘g’)
fooXX
regexp_replace(‘foobarbaz’, ‘b(..)’, ‘X\1Y’, ‘g’)
fooXarYXazY

Question 33

substring()

Answer 33

The substring function with two parameters, substring(string from pattern), provides extraction of a substring that matches a POSIX regular expression pattern.

It returns null if there is no match, otherwise the first portion of the text that matched the pattern.

But if the pattern contains any parentheses, the portion of the text that matched the first parenthesized subexpression (the one whose left parenthesis comes first) is returned.

You can put parentheses around the whole expression if you want to use parentheses within it without triggering this exception. If you need parentheses in the pattern before the subexpression you want to extract, see the non-capturing parentheses described below.

Examples:
substring(‘foobar’ from ‘o.b’) oob
substring(‘foobar’ from ‘o(.)b’) o

Question 34

%

Answer 34

Any string (using LIKE and SIMILAR TO)

Example:
c%
Matches:
chart, articulation, crate