I'm trying to query a table with a like statement. Is _ considered a wildcard symbol in postgres? Would
select * from table where field1 like '%_123_%'
return the same thing as
select * from table where field1 like '%123%'
Here is an example from the official documentation regarding wildcards in Postgres:
'abc' LIKE 'abc' true
'abc' LIKE 'a%' true
'abc' LIKE '_b_' true
'abc' LIKE 'c' false
_ is a wildcard for one character, while % is a wildcard for multiple characters.
Yes, _ is a wildcard symbol that matches one character. It can't be an empty match, so no, those statements are not the same. The first requires the string be at least 5 characters long while the second only requires 3 characters.
If you're familiar with regexes, %123% is equivalent to .*123.*, while %_123_% is equivalent to .+123.+.
From the PostgreSQL manual:
To match a literal underscore or percent sign without matching other characters, the respective character in pattern must be preceded by the escape character. The default escape character is the backslash but a different one can be selected by using the ESCAPE clause. To match the escape character itself, write two escape characters.
yes
_ matches one char while % matches lots of chars.
Related
I have a query like this which is not retrieving the values from DB table even if the required value exist there.
Here's the query, which return zero rows:
Select * from SitePanel_FieldValue WHere SiteFieldIdfk =111
And SiteFieldvalue like '%!##$%&*()-_=+{}|:"<>?[]\;'',./%'
Following is the value in the table:
'!##$%&*()-_=+{}|:"<>?[]\;'',./'
When I run the query without ";" it is returning the value.
Can any one help me in figuring this out?
Thanks
Ritu
You are using multiple characters which are reserved when using LIKE statement.
i.e. %, _, []
Use the escape character clause (where I have used backtick to treat special characters as regular) such as
Select * from SitePanel_FieldValue WHere SiteFieldIdfk =111
And SiteFieldvalue like '%!##$`%&*()-`_=+{}|:"<>?`[`]\;'',./%' escape '`'
The value in your table is:
!##$%&*()-_=+{};; :"<>?[]\;'',./
And the one in the like is:
(!##$%&*()-_=+{};;
Starting with ( it will never match, also you should scape the percent (%) in the middle of the string like this:
Select *
FROM SitePanel_FieldValue
WHERE SiteFieldIdfk =111
AND SiteFieldvalue like '%!##$\%&*()-_=+{};;%' ESCAPE '\'
The problem is your brackets ([]), it has nothing to do with semicolons. If we remove the brackets, the above works:
SELECT CASE WHEN '!##$%&*()-_=+{}|:"<>?\;'',./' LIKE '%!##$%&*()-_=+{}|:"<>?\;'',./%' THEN 1 END AS WithoutBrackets,
CASE WHEN '!##$%&*()-_=+{}|:"<>?[]\;'',./' LIKE '%!##$%&*()-_=+{}|:"<>?[]\;'',./%' THEN 1 END AS WithBrackets
Notice that WithoutBrackets returns 1, where as WithBrackets returns NULL.
Brackets in a LIKE are to denote a pattern. For example SomeExpress LIKE '[ABC]' would match the characters, A, B, and C. If you are going to include special characters, you need to ESCAPE them. You have both brackets, a percent sign (%) and an underscore (_) you need to escape. You don't need to escape the hyphen (-), as it doesn't appear in a pattern (for example [A-Z]). I choose to use a backtick as the ESCAPE character, as it doesn't appear in your string, and demonstrate with a CASE expression again:
SELECT CASE WHEN '!##$%&*()-_=+{}|:"<>?[]\;'',./' LIKE '%!##$`%&*()-`_=+{}|:"<>?`[`]\;'',./%' ESCAPE '`' THEN 1 END;
If you wanted to use a backslash (\ ), which many do, you would need to also escape the backslash in your string:
SELECT CASE WHEN '!##$\%&*()-_=+{}|:"<>?[]\;'',./' LIKE '%!##$%&*()-\_=+{}|:"<>?\[\]\\;'',./%' ESCAPE '\' THEN 1 END;
db<>fiddle
I think the issue is actually with the backslash. This is an escape character and so if you want it to be included, you have to put it in twice.
Select * from SitePanel_FieldValue WHere SiteFieldIdfk =111
And SiteFieldvalue like '%!##$%&*()-_=+{}|:"<>?[]\\;'',./%'
I have an nvarchar(50) column myCol with values like these 16-digit, alphanumeric values, starting with '0':
0b00d60b8d6cfb19, 0b00d60b8d6cfb05, 0b00d60b8d57a2b9
I am trying to delete rows with myCol values that don't match those 3 criteria.
By following this article, I was able to select the records starting with '0'. However, despite the [a-z0-9] part of the regex, it also keeps selecting myCol values containing special characters like 00-d#!b8-d6/f&#b. Below is my select query:
SELECT * from Table
WHERE myCol LIKE '[0][a-z0-9]%' AND LEN(myCol) = 16
How should the expression be changed to select only rows with myCol values that don't contain special characters?
If the value must only contain a-z and digits, and must start with a 0 you could use the following:
SELECT *
FROM (VALUES(N'0b00d60b8d6cfb19'),
(N'0b00d60b8d6cfb05'),
(N'0b00d60b8d57a2b9'),
(N'00-d#!b8-d6/f&#b'))V(myCol)
WHERE V.myCol LIKE '0%' --Checks starts with a 0
AND V.myCol NOT LIKE '%[^0-9A-z]%' --Checks only contains alphanumerical characters
AND LEN(V.myCol) = 16;
The second clause works as the LIKE will match any character that isn't an alphanumerical character. The NOT then (obviously) reverses that, meaning that the expression only resolves to TRUE when the value only contains alphanumerical characters.
Pattern matching in SQL Server is not awesome, and there is currently no real regex support.
The % in your pattern is what is including the special characters you show in your example. The [a-z0-9] is only matching a single character. If your character lengths are 16 and you're only interested in letters and numbers then you can include a pattern for each one:
SELECT *
FROM Table
WHERE myCol LIKE '[0][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9][a-z0-9]';
Note: you don't need the AND LEN(myCol) = 16 with this.
I need to find rows where the phone number field contains unexpected characters.
Most of the values in this field look like:
123456-7890
This is expected. However, we are also seeing character values in this field such as * and #.
I want to find all rows where these unexpected character values exist.
Expected:
Numbers are expected
Hyphen with numbers is expected (hyphen alone is not)
NULL is expected
Empty is expected
Tried this:
WHERE phone_num is not like ' %[0-9,-,' ' ]%
Still getting rows where phone has numbers.
from https://regexr.com/3c53v address you can edit regex to match your needs.
I am going to use example regex for this purpose
select * from Table1
Where NOT REGEXP_LIKE(PhoneNumberColumn, '^[+]*[(]{0,1}[0-9]{1,4}[)]{0,1}[-\s\./0-9]*$')
You can use translate()
...
WHERE translate(Phone_Number,'a1234567890-', 'a') is NOT NULL
This will strip out all valid characters leaving behind the invalid ones. If all the characters are valid, the result would be NULL. This does not validate the format, for that you'd need to use REGEXP_LIKE or something similar.
You can use regexp_like().
...
WHERE regexp_like(phone_num, '[^ 0123456789-]|^-|-$')
[^ 0123456789-] matches any character that is not a space nor a digit nor a hyphen. ^- matches a hyphen at the beginning and -$ on the end of the string. The pipes are "ors" i.e. a|b matches if pattern a matches of if pattern b matches.
Oracle has REGEXP_LIKE for regex compares:
WHERE REGEXP_LIKE(phone_num,'[^0-9''\-]')
If you're unfamiliar with regular expressions, there are plenty of good sites to help you build them. I like this one
I can guesss it may be easy to answer type question but I am facing it first time, so any help will be more appreciated.
My Query:
SELECT remarks FROM enroll WHERE remarks LIKE 'REC_%'
OUTPUT:
remarks
REC_59161
Reclassify Hedge
Expected Output is only REC_59161. Yes _ is used for matching any single character but I am just looking for achieving my expected output.
_ is a wildcard Character. So that you have to escape it using [].
Query
select remarks
from enroll
where remarks like 'REC[_]%';
The underscore _ character is actually a special character with the LIKE operator, as are %, [] and ^:
https://learn.microsoft.com/en-us/sql/t-sql/language-elements/like-transact-sql
In that article, you'll see that an underscore _ matches any single character.
Use the ESCAPE keyword to define an escape character to allow you to escape the pattern-matching characters. We can use ! as the escape character, so:
WHERE remarks LIKE 'REC!_%' ESCAPE '!'
_ is a wildcard character, Try this :
declare #enroll table (remarks varchar(50));
insert into #enroll values ('REC_59161') , ('Reclassify Hedge');
SELECT remarks FROM #enroll WHERE remarks LIKE 'REC[_]%';
Demo
There are two issues:
It seems that the column is case insensitive, see Is the LIKE operator case-sensitive with MS SQL server? for details. That's why Rec in Reclassify Hedge fits REC in the Like
_ (as well as %) is a wild card, you should escape _ in the pattern
Query:
SELECT remarks
FROM enroll
WHERE remarks LIKE 'REC*_%' ESCAPE '*' /* SQL 92 standard */
http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
uses the triadic operator LIKE (or the inverse, NOT
LIKE), operating on three character strings and returning a Boolean.
LIKE determines whether or not a character string "matches" a given
"pattern" (also a character string). The characters '%' (percent)
and '_' (underscore) have special meaning when they occur in the
pattern. The optional third argument is a character string
containing exactly one character, known as the "escape character", for
use when a percent or underscore is required in the pattern without
its special meaning.
I have this situation on my azure database where I need to search for any rows that contains the _ character. This is a special character on the database so I try to escape it but I get every row as a result.
select * from table where fieldColumn like '%_%'
will return everything on the table
select * from table where fieldColumn like '%\_%'
returns nothing
select * from table where fieldColumn = '_'
works
so how can i get that row that has only one _ and all the other ones that may have the _ on the string?
You can set whatever escape character you want, like this:
select * from table where fieldColumn like '%!_%' ESCAPE '!'
Here I am using the ! as an escape character to tell SQL Server to treat the following character, the _ , as a string literal.
See the documentation for more info: http://technet.microsoft.com/en-us/library/ms179859.aspx
select * from table where fieldColumn like '%_%' escape '\';
LIKE:
escape_character
Is a character that is put in front of a wildcard character to indicate that the wildcard should be interpreted as a regular character and not as a wildcard. escape_character is a character expression that has no default and must evaluate to only one character.