Strings and text
Introduction
Strings, character data types, or text are part of every conceivable system. Manipulating and outputting text is a very important topic that is required for many different types of systems that you work with. This section provides an overview of the YugabyteDB SQL API's extensive text capabilities.
The examples use the Retail Analytics sample dataset.
Character data types
With PostgreSQL, the use of different character data types has a historical aspect. YugabyteDB — being a more recent implementation — has no such history. Consider keeping your use of character data types simple, ideally just 'text', or 'varchar(n)' if you require a restricted length. Using text and then verifying the length of a character string allows you to develop your own approach to managing this scenario, rather than encountering errors by exceeding some arbitrary length.
If you use char(n), character(n), or varchar(n), then the limitation will be the number you assign, which cannot exceed 10,485,760. For unlimited length, use a character data type without a length description, such as 'text'. However, if you have specific requirements to ignore trailing spaces, then you may wish to consider using char(n).
For more information on character data types, refer to Data types. Note that YugabyteDB implements the data type aliases and that is what is used here.
The following example shows a few ways to work with different data types:
./bin/ysqlsh
ysqlsh (11.2)
Type "help" for help.
yugabyte=# create table text_columns(a_text text, a_varchar varchar, a_char char, b_varchar varchar(10), b_char char(10));
CREATE TABLE
yugabyte=# insert into text_columns values('abc ', 'abc ', 'abc ', 'abc ', 'abc ');
ERROR: value too long for type character(1)
yugabyte=# insert into text_columns values('abc ', 'abc ', 'a', 'abc ', 'abc ');
INSERT 0 1
yugabyte=# select * from text_columns
where a_text like 'ab__' and a_varchar like 'ab__'
and b_varchar like 'ab__';
a_text | a_varchar | a_char | b_varchar | b_char
--------+-----------+--------+-----------+------------
abc | abc | a | abc | abc
yugabyte=# select * from text_columns
where a_text like 'ab__' and a_varchar like 'ab__'
and b_varchar like 'ab__' and b_char like 'ab__';
a_text | a_varchar | a_char | b_varchar | b_char
--------+-----------+--------+-----------+--------
(0 rows)
yugabyte=# select length(a_text) as a_text, length(a_varchar) as a_varchar, length(a_char) as a_char,
length(b_varchar) as b_varchar, length(b_char) as b_char
from text_columns;
a_text | a_varchar | a_char | b_varchar | b_char
--------+-----------+--------+-----------+--------
4 | 4 | 1 | 4 | 3
Notice that the column b_char does not contain a trailing space and this could impact your SQL. In addition, if you specify a maximum length on the column definition, the SQL can also generate errors, so you have to either manually truncate your input values or introduce error handling.
Casting
When you are working with text that has been entered by users through an application, ensure that YugabyteDB understands that it is working with a text input. All values should be cast unless they can be trusted due to other validation measures that have already occurred.
The following example shows the impacts of casting:
yugabyte=# select cast(123 AS TEXT), cast('123' AS TEXT), 123::text, '123'::text;
text | text | text | text
------+------+------+------
123 | 123 | 123 | 123
yugabyte=# select tablename, hasindexes AS nocast, hasindexes::text AS casted
from pg_catalog.pg_tables
where tablename in('pg_default_acl', 'sql_features');
tablename | nocast | casted
----------------+--------+--------
pg_default_acl | t | true
sql_features | f | false
T he column 'hasindexes' is a Boolean data type and by casting it to text, you receive a text result of true or false.
Manipulating text
Many functions can be applied to text. In the examples that follow, the functions are classified into logical groupings - in many cases the capability of the functions overlap and personal choice determines how you approach solving the problem.
The focus here is to quickly show how each of the functions can be used, along with some examples.
The example assumes that you have created and connected to the yb_demo database with the Retail Analytics sample dataset.
Altering the appearance of text
yb_demo =# select lower('hELLO world') AS LOWER,
upper('hELLO world') AS UPPER,
initcap('hELLO world') AS INITCAP;
lower | upper | initcap
-------------+-------------+-------------
hello world | HELLO WORLD | Hello World
yb_demo =# select quote_ident('ok') AS EASY, quote_ident('I am OK') AS QUOTED, quote_ident('I''m not OK') AS DOUBLE_QUOTED, quote_ident('') AS EMPTY_STR, quote_ident(null) AS NULL_QUOTED;
easy | quoted | double_quoted | empty_str | null_quoted
------+-----------+---------------+-----------+-------------
ok | "I am OK" | "I'm not OK" | "" |
yb_demo =# select quote_literal('ok') AS EASY, quote_literal('I am OK') AS QUOTED, quote_literal('I''m not OK') AS DOUBLE_QUOTED, quote_literal('') AS EMPTY_STR, quote_literal(null) AS NULL_QUOTED;
easy | quoted | double_quoted | empty_str | null_quoted
------+-----------+---------------+-----------+-------------
'ok' | 'I am OK' | 'I''m not OK' | '' |
yb_demo =# select quote_nullable('ok') AS EASY, quote_nullable('I am OK') AS QUOTED, quote_nullable('I''m not OK') AS DOUBLE_QUOTED, quote_nullable('') AS EMPTY_STR, quote_nullable(null) AS NULL_QUOTED;
easy | quoted | double_quoted | empty_str | null_quoted
------+-----------+---------------+-----------+-------------
'ok' | 'I am OK' | 'I''m not OK' | '' | NULL
Use quote_ident to parse identifiers in SQL like column names and quote_nullable as a string literal that may also be a null.
Parsing raw text
You can use "dollar sign quoting" to parse raw text — any text enclosed in dollar sign ($) quotations are treated as a raw literal. The starting and ending markers do not need to be identical, but must start and end with a dollar sign. Consider the following examples:
yb_demo=# select $$%&*$&$%7'\67458\''""""';;'\//\/\/\""'/'''''"""""'''''''''$$;
?column?
-----------------------------------------------------------
%&*$&$%7'\67458\''""""';;'\//\/\/\""'/'''''"""""'''''''''
yb_demo=# select $__unique_$ Lots of space
yb_demo=# and multi-line too $__unique_$;
?column?
----------------------------------------------
Lots of space +
and multi-line too
yb_demo=# select $$first$$ AS "F1", $$second$$ AS "F2";
F1 | F2
-------+--------
first | second
Padding and trimming
Some values need to be padded for formatting purposes, and lpad() and rpad() ('left pad' and 'right pad', respectively) are meant for this purpose. They are normally used with spaces, but you can pad using anything, including more than a single character. For example, you can pad with underscores (_) or spaced dots . . .. You do not specify how much to pad, but the maximum length to pad. Therefore, if your value is already as long as your maximum length, then no padding is required. Note that this can cause truncation if your field is longer than the maximum length specified.
The reverse of padding is trimming, which removes spaces if found. The following examples use padding and trimming to achieve the results required:
yb_demo=# select name, lpad(name, 10), rpad(name, 15) from users order by name limit 5;
name | lpad | rpad
-------------------+------------+-----------------
Aaron Hand | Aaron Hand | Aaron Hand
Abbey Satterfield | Abbey Satt | Abbey Satterfie
Abbie Parisian | Abbie Pari | Abbie Parisian
Abbie Ryan | Abbie Ryan | Abbie Ryan
Abby Larkin | Abby Larki | Abby Larkin
yb_demo=# select name, lpad(name, 20), rpad(name, 20) from users order by name limit 5;
name | lpad | rpad
-------------------+----------------------+----------------------
Aaron Hand | Aaron Hand | Aaron Hand
Abbey Satterfield | Abbey Satterfield | Abbey Satterfield
Abbie Parisian | Abbie Parisian | Abbie Parisian
Abbie Ryan | Abbie Ryan | Abbie Ryan
Abby Larkin | Abby Larkin | Abby Larkin
yb_demo=# select name, lpad(name, 20, '. '), rpad(name, 20, '.') from users order by name limit 5;
name | lpad | rpad
-------------------+----------------------+----------------------
Aaron Hand | . . . . . Aaron Hand | Aaron Hand..........
Abbey Satterfield | . .Abbey Satterfield | Abbey Satterfield...
Abbie Parisian | . . . Abbie Parisian | Abbie Parisian......
Abbie Ryan | . . . . . Abbie Ryan | Abbie Ryan..........
Abby Larkin | . . . . .Abby Larkin | Abby Larkin.........
yb_demo=# select repeat(' ', ((x.maxlen-length(u.name))/2)::int) || rpad(u.name, x.maxlen) AS "cname"
from users u,
(select max(length(a.name))::int AS maxlen from users a) AS x;
cname
------------------------------
Stewart Marks
Regan Corkery
Domenic Daugherty
Winfield Donnelly
Theresa Kertzmann
Terrence Emmerich
Hudson Jacobi
Aidan Hagenes
Virgil Schowalter
Rahul Kreiger
Wilhelmine Erdman
Elwin Okuneva
Maximillian Dickinson
Lucie Cormier
Alexandrine Rosenbaum
Jayne Breitenberg
Alexandria Schowalter
Augustine Runolfsdottir
Mathilde Weissnat
Theresa Grant
...
yb_demo=# select x.RawDay, length(x.RawDay) AS RawLen, x.TrimDay, length(x.TrimDay) AS TrimLen,
x.LTrimDay, length(x.LTrimDay) AS LTrimLen, x.RTrimDay, length(x.RTrimDay) AS RTrimLen
from (select to_char(generate_series, 'Day') AS RawDay,
trim(to_char(generate_series, 'Day')) AS TrimDay,
ltrim(to_char(generate_series, 'Day')) AS LTrimDay,
rtrim(to_char(generate_series, 'Day')) AS RTrimDay
from generate_series(current_date, current_date+6, '1 day')) AS x;
rawday | rawlen | trimday | trimlen | ltrimday | ltrimlen | rtrimday | rtrimlen
-----------+--------+-----------+---------+-----------+----------+-----------+----------
Wednesday | 9 | Wednesday | 9 | Wednesday | 9 | Wednesday | 9
Thursday | 9 | Thursday | 8 | Thursday | 9 | Thursday | 8
Friday | 9 | Friday | 6 | Friday | 9 | Friday | 6
Saturday | 9 | Saturday | 8 | Saturday | 9 | Saturday | 8
Sunday | 9 | Sunday | 6 | Sunday | 9 | Sunday | 6
Monday | 9 | Monday | 6 | Monday | 9 | Monday | 6
Tuesday | 9 | Tuesday | 7 | Tuesday | 9 | Tuesday | 7
The preceding example shows how you can center text and the trim example shows the impacts of the different trims on a value that is padded. Note that the 'Day' value is right-padded to 9 characters, which is why a left-trim has no impact on the field length at all; only the right-trim or a 'full' trim will remove spaces.
Escaping
You can also state that a text value is 'escaped' by prefixing with an 'e' or 'E'. For example:
yb_demo=# select E'I''ve told YugabyteDB that this is an escaped string\n\tso I can specify escapes safely' as escaped_text;
escaped_text
---------------------------------------------------
I've told YugabyteDB that this is an escaped string+
so I can specify escapes safely
yb_demo=# select E'a\\b/c\u00B6' as escaped_txt, 'a\\b/c\u00B6' as raw_txt;
escaped_txt | raw_txt
-------------+--------------
a\b/c¶ | a\\b/c\u00B6
Note
\n refers to a new line, and \t is a tab, hence the formatted result.
Encoding and converting text
YugabyteDB also has DECODE and ENCODE for decoding and encoding from, or to, binary data. It caters for 'base64', 'hex', and 'escape' representations. Decode gives the output in BYTEA data type. Additionally, you can use the TO_HEX command to convert an ASCII number to its digital representation.
Joining strings
You can concatenate strings of text in several different ways. For robustness, you should ensure that everything being passed is interpreted as text (by casting) so that unexpected results do not appear in edge cases. The following examples show that YugabyteDB is lenient in passing in variables, but you should implement more robust casting for proper treatment of strings:
yb_demo=# select 'one' || '-' || 2 || '-one' AS "121";
121
-----------
one-2-one
yb_demo=# select 2 || '-one-one' AS "211";
211
-----------
2-one-one
yb_demo=# select 1 || '-one' || repeat('-two', 2) AS "1122";
1122
---------------
1-one-two-two
yb_demo=# select 1::text || 2::text || 3::text AS "123";
123
-----
123
yb_demo=# select 1 || 2 || 3 AS "123";
ERROR: operator does not exist: integer || integer
LINE 1: select 1 || 2 || 3 AS "123";
^
HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
yb_demo=# select concat(1,2,3) AS "123";
123
-----
123
yb_demo=# select concat_ws(':', 1,2,3) AS "123 WS";
123 WS
--------
1:2:3
(1 row)
yb_demo =# select left(vendor,1) AS V, string_agg(distinct(category), ', ' ORDER BY category) AS CATEGORIES
from products group by left(vendor,1) order by 1;
v | categories
---+----------------------------------
A | Doohickey, Gadget, Gizmo
B | Doohickey, Gadget, Gizmo, Widget
C | Doohickey, Gadget, Gizmo, Widget
D | Gadget, Gizmo, Widget
E | Gadget, Gizmo, Widget
F | Doohickey, Gadget, Gizmo, Widget
G | Doohickey, Gadget, Widget
H | Doohickey, Gadget, Gizmo, Widget
I | Gizmo, Widget
J | Doohickey, Gadget, Gizmo, Widget
K | Doohickey, Gadget, Gizmo, Widget
L | Doohickey, Gadget, Gizmo, Widget
M | Doohickey, Gadget, Gizmo, Widget
N | Doohickey, Gadget, Widget
O | Doohickey, Gadget, Gizmo, Widget
P | Doohickey, Gadget, Gizmo, Widget
Q | Doohickey
R | Doohickey, Gadget, Gizmo, Widget
S | Doohickey, Gadget, Gizmo, Widget
T | Gizmo, Widget
U | Gadget
V | Doohickey, Widget
W | Doohickey, Gadget, Gizmo, Widget
Z | Gizmo
The preceding example uses the LEFT function, but the string_agg function is best used by an input of a series or a set of data as done in SQL rows. The example shows how the aggregated string has its own order by compared to the outer SQL which is the vendors being classified A-Z.
The REVERSE function reverses the contents of text as shown in the following example:
yb_demo=# select reverse(to_char(current_date, 'DD-MON-YYYY'));
reverse
-------------
9102-LUJ-92
Parsing user input
To minimise the impact of unexpected data that is typical of a SQL injection attack, you can use the FORMAT function to parse user input as parameters to a SQL statement. The most popular method is to use the EXECUTE command in a procedure as this is not available at the YSQL command prompt, only in the YSQL PL/pgSQL environment. The FORMAT command is used to finalise the complete SQL statement which is passed to EXECUTE to run. As you are not simulating YSQL PL/pgSQL here, the following example illustrates how to use the FORMAT function only:
yb_demo=# select format('Hello %s, today''s date is %s', 'Jono', to_char(current_date, 'DD-MON-YYYY'), 'discarded');
format
-----------------------------------------
Hello Jono, today's date is 29-JUL-2019
yb_demo=# select format('On this day, %2$s, %1$s was here', 'Jono', to_char(current_date, 'DD-MON-YYYY'));
format
-----------------------------------------
On this day, 29-JUL-2019, Jono was here
yb_demo=# select format('SELECT %2$I, %3$I from %1$I where name = %4$L', 'users', 'birth_date', 'email', 'Brody O''Reilly');
format
--------------------------------------------------------------------
SELECT birth_date, email from users where name = 'Brody O''Reilly'
Substituting text
Substituting text with other text can be a complex task, as you need to fully understand the scope of the data that the functions can be subject to. A common occurrence is failure due to an unexpected value being passed through, like NULL, an empty string '', or a value that YugabyteDB would interpret as a different data type like true or 3.
The treatment of nulls in mathematical operations is often problematic, as are string joins as joining a null to a value results in a null. Coalescing the inputs avoids these issues as shown in the following examples:
yb_demo=# select trunc(avg(coalesce(discount,0))::numeric,3) AS "COALESCED", trunc(avg(discount)::numeric,3) AS "RAW" from orders;
COALESCED | RAW
-----------+-------
0.530 | 5.195
yb_demo=# select 'Hello ' || null AS GREETING, 'Goodbye ' || coalesce(null, 'Valued Customer') AS GOODBYE;
greeting | goodbye
----------+-------------------------
| Goodbye Valued Customer
The preceding example shows how substituting when null can have a significant impact on the results you achieve, or even the behaviour of your application.
The following example demonstrates ways to change existing text using other text.
yb_demo=# select overlay(password placing 'XXXXXXXXXXXXXXX' from 1 for length(password)) AS SCRAMBLED from users limit 5;
scrambled
-----------------
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
yb_demo=# select regexp_replace('Hi my number is +999 9996-1234','[[:alpha:]]','','g');
regexp_replace
--------------------
+999 9996-1234
yb_demo=# select 'I think I can hear an ' || repeat('echo.. ', 3) AS CLICHE;
cliche
---------------------------------------------
I think I can hear an echo.. echo.. echo..
yb_demo=# select replace('Gees I love Windows', 'Windows', 'Linux') AS OBVIOUS;
obvious
-------------------
Gees I love Linux
The REGEXP_REPLACE function along with the other REGEX functions require an entire chapter to themselves given the sophistication that can be achieved. The preceding example strips out all characters of the alphabet and replaces them with an empty string. The 'g' flag is 'global', and results in the replacement occurring throughout the entire string; without the 'g' flag the replace stops after the first substitution. Note that the result contains spaces which is why it appears odd. You might think that this example shows an extraction of non-alphabetical characters, but it is just replacing them with an empty string.
Extracting text
There are several ways to extract text from text; in some cases it might be part of 'cleaning' the text. (Removing leading or trailing spaces is covered by the trim functions shown in a preceding section.) The remaining functions here show how parts of text can be manipulated.
yb_demo=# select left('123456', 3);
left
------
123
yb_demo=# select right('123456', 3);
right
-------
456
yb_demo=# select substr('123456', 3);
substr
--------
3456
yb_demo=# select substr('123456', 3, 2);
substr
--------
34
yb_demo=# select substr('123456', position('4' in '123456')+1, 2);
substr
--------
56
yb_demo=# select substring('123456', position('4' in '123456')+1, 2);
substring
-----------
56
yb_demo=# select replace(substr(email, position('@' in email)+1, (length(email)
-position('.' in substr(email, position('@' in email)+1)))), '.com', '') AS "Domain", count(*)
from users
group by 1;
Domain | count
---------+-------
hotmail | 813
yahoo | 838
gmail | 849
The command SUBSTRING has overloaded equivalents that accept POSIX expressions. The preceding example shows a basic use of SUBSTRING (which can also be used as SUBSTR). It is recommended to only use the full SUBSTRING command when using POSIX.
Regular expressions
A full description of regular expressions requires its own comprehensive documentation that is not covered here. The following example illustrates their use:
yb_demo=# select name as Fullname, regexp_match(name, '(.*)(\s+)(.*)') AS "REGEXED Name",
(regexp_match(name, '(.*)(\s+)(.*)'))[1] AS "First Name",
(regexp_match(name, '(.*)(\s+)(.*)'))[3] AS "Last Name"
from users limit 5;
fullname | REGEXED Name | First Name | Last Name
----------------+----------------------+------------+-----------
Jacinthe Rowe | {Jacinthe," ",Rowe} | Jacinthe | Rowe
Walter Mueller | {Walter," ",Mueller} | Walter | Mueller
Fatima Murphy | {Fatima," ",Murphy} | Fatima | Murphy
Paxton Mayer | {Paxton," ",Mayer} | Paxton | Mayer
Mellie Wolf | {Mellie," ",Wolf} | Mellie | Wolf
In the preceding example, you are asking the 'name' column to be delimited by the existence of a space (\s) and then reporting the first and third set of text reported by the match. The regular expression returns a text array, not a text value, and thus you have to reference the array index to access the value as text. Note that this SQL would be very vulnerable to errors caused by data entry, including a middle name or missing either a first or last name would cause errors.
Now, let's look at some manipulation and splitting of text so that you can process it in pieces. The following example uses a sample extract from a bank file that is used for processing payments. This example could apply if the entire file was uploaded as a single text entry into a table and you select it and then process it.
yb_demo=# create table bank_payments(bank_file text);
CREATE TABLE
yb_demo=# insert into bank_payments values($$"CMGB","1.0","95012141352105","999999","30128193018492","20","","GBP","B","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","","909170/1","AB"
"CMGB","1.0","95012141352105","999999","95012113864863","10.00","","GBP","B","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","Remitters name 18","Tech ref for automatic processing5","AT","/t.x",
"CMGB","1.0","95012141352105","","30128193018492","21","","GBP","C","Beneficiary name18","Txt on senders acc","","Txt for credit acc","","","","","909175/0","AB"
"CMGB","1.0","95012141352105","","30128193018492","22","","GBP","I","Beneficiary name18","Txt on senders acc","text","","","","","","909175/1","AB"
"CMGB","1.0","95012141352105","","30128193018492","23","","GBP","F","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","","909171/0","AB"$$);
INSERT 0 1
yb_demo=# select regexp_split_to_table(bank_file, chr(10)) from bank_payments;
regexp_split_to_table
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
"CMGB","1.0","95012141352105","999999","30128193018492","20","","GBP","B","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","","909170/1","AB"
"CMGB","1.0","95012141352105","999999","95012113864863","10.00","","GBP","B","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","Remitters name 18","Tech ref for automatic processing5","AT","/t.x",
"CMGB","1.0","95012141352105","","30128193018492","21","","GBP","C","Beneficiary name18","Txt on senders acc","","Txt for credit acc","","","","","909175/0","AB"
"CMGB","1.0","95012141352105","","30128193018492","22","","GBP","I","Beneficiary name18","Txt on senders acc","text","","","","","","909175/1","AB"
"CMGB","1.0","95012141352105","","30128193018492","23","","GBP","F","Beneficiary name18","Txt on senders acc","Txt for credit acc","","","","","","909171/0","AB"
yb_demo=# select split_part(f.line, ',' , 8) AS "currency",
split_part(f.line, ',' , 5) AS "Account"
from (select regexp_split_to_table(bank_file, chr(10)) AS "line" from bank_payments) AS f;
currency | Account
----------+------------------
"GBP" | "30128193018492"
"GBP" | "95012113864863"
"GBP" | "30128193018492"
"GBP" | "30128193018492"
"GBP" | "30128193018492"
Remember to drop the table 'bank_payments' if it is no longer required.
yb_demo=# select reverse(translate(replace(lower(i.input), ' ', ''),
'abcdefghijklmnopqrstuvwxyz',
'A8Cd349h172!mN0pQr$TuVw*yZ')) AS "simplePWD"
from (select 'type a word here' AS "input") AS i;
simplePWD
---------------
3r3hdr0wA3pyT
The preceding TRANSLATE command replaces multiple different characters in a single command, which can be useful. In the example, the 'a' is replaced with a 'A', and 'b' is replaced with the number '8', and so forth.
Obtaining information about text
Rather than format or change the contents of text, you often might want to understand particular attributes of the text. The following examples use commands to return information about the text:
yb_demo=# select x.c AS CHAR, ascii(x.c) AS ASCII
from (select regexp_split_to_table(i.input, '') AS "c"
from (select 'hello' AS input) AS i) AS x;
char | ascii
------+-------
h | 104
e | 101
l | 108
l | 108
o | 111
yb_demo=# select bit_length('hello'), char_length('hello'), octet_length('hello');
bit_length | char_length | octet_length
------------+-------------+--------------
40 | 5 | 5
yb_demo=# select array_agg(chr(ascii(x.c))) AS "CHAR"
from (select regexp_split_to_table(i.input, '') AS "c"
from (select 'hello' AS input) AS i) AS x;
CHAR
-------------
{h,e,l,l,o}
yb_demo=# select avg(length(name))::int AS AVG_LENGTH from users;
avg_length
------------
14
yb_demo=# select name from users
where position('T' in name) > 2
and position('p' in name) = length(name)
order by name;
name
-----------------
Cory Tromp
Demario Tromp
Demetris Tromp
Deon Tromp
Emelia Tromp
Ivah Tromp
Jany Torp
Jared Tromp
Judd Tromp
Larue Torp
Magdalen Torp
Margarita Tromp
Marjolaine Torp
Patrick Torp
Porter Tromp
Rebeka Tromp
yb_demo=# select name, position('ar' in name) AS posn, strpos(name, 'ar') as strpos
from users
where strpos(name, 'ark') > 0
order by name desc limit 10;
name | posn | strpos
----------------+------+--------
Yasmin Stark | 10 | 10
Veronica Stark | 12 | 12
Tamia Larkin | 8 | 8
Stewart Marks | 5 | 5
Ryann Parker | 8 | 8
Rudy Larkin | 7 | 7
Rodolfo Larkin | 10 | 10
Novella Marks | 10 | 10
Markus Hirthe | 2 | 2
Mark Klein | 2 | 2
yb_demo=# select m.name
from (select to_char(generate_series, 'Month') AS name
from generate_series(current_date-364, current_date, '1 month')) AS m
where starts_with(m.name, 'J');
name
-----------
January
June
July
Something a bit more advanced
If you like a bit of a challenge, the following example URL escapes a string. There is some more room for tweaking in its current form, that is left for you to do.
yugabyte=# select string_agg(case
when to_hex(ascii(x.arr::text))::text
in('20','23','24','25','26','40','60','2b','2c','2f','3a','3b','3c','3d','3e','3f',
'5b','5c','5d','5e','7b','7c','7d') then '%' || to_hex(ascii(x.arr::text))::text
else x.arr
end, '') AS "url_escaped"
from (select regexp_split_to_table('www.url.com/form?name="My name"&dob="1/1/2000"&email="[email protected]"', '')) AS x (arr);
url_escaped
------------------------------------------------------------------------------------------------
www.url.com%2fform%3fname%3d"My%20name"%26dob%3d"1%2f1%2f2000"%26email%3d"hello%40example.com"