I have a row in cassandra table where one of the column has a trailing space which looks like "someval\xa0"
How can i write a cql query to escape the unicode character \xa0, basically i'm trying to delete the row from the table.
Tried with \, single quotes, $$$ but no luck..
delete * from testkeyspace.testtable where username="someval\xa0"
delete * from testkeyspace.testtable where username=$$$someval\xa0$$$
delete * from testkeyspace.testtable where username=\\someval\xa0\\
Text constants should be wrapped into single quotes: 'someval\xa0' (see doc for reference).
Related
I inserted a bunch of rows with a text field like content='...\n...\n...'.
I didn't use e in front, like conent=e'...\n...\n..., so now \n is not actually displayed as a newline - it's printed as text.
How do I fix this, i.e. how to change every row's content field from '...' to e'...'?
The syntax variant E'string' makes Postgres interpret the given string as Posix escape string. \n encoding a newline is only one of many interpreted escape sequences (even if the most common one). See:
Insert text with single quotes in PostgreSQL
To "re-evaluate" your Posix escape string, you could use a simple function with dynamic SQL like this:
CREATE OR REPLACE FUNCTION f_eval_posix_escapes(INOUT _string text)
LANGUAGE plpgsql AS
$func$
BEGIN
EXECUTE 'SELECT E''' || _string || '''' INTO _string;
END
$func$;
WARNING 1: This is inherently unsafe! We have to evaluate input strings dynamically without quoting and escaping, which allows SQL injection. Only use this in a safe environment.
WARNING 2: Don't apply repeatedly. Or it will misinterpret your actual string with genuine \ characters, etc.
WARNING 3: This simple function is imperfect as it cannot cope with nested single quotes properly. If you have some of those, consider instead:
Unescape a string with escaped newlines and carriage returns
Apply:
UPDATE tbl
SET content = f_eval_posix_escapes(content)
WHERE content IS DISTINCT FROM f_eval_posix_escapes(content);
db<>fiddle here
Note the added WHERE clause to skip updates that would not change anything. See:
How do I (or can I) SELECT DISTINCT on multiple columns?
Use REPLACE in an update query. Something like this: (I'm on mobile so please ignore any typo or syntax erro)
UPDATE table
SET
column = REPLACE(column, '\n', e'\n')
I need to find all the instances of the string: "TEXT\00" (nvarchar type field)
select * from table
where contains(TEXT_Extracted, '"TEXT\00"')
However, this returns the instances of TEXT fallowed by space ("TEXT ").
I am using T-SQL 2008.
select * from table
where contains(TEXT_Extracted, '"TEXT$\00"') ESCAPE '$'
I have a table with camelCased column names (which I now deeply regret). If I use double quotation marks around the column names as part of the SELECT clause, they work fine, e.g. SELECT "myCamelCasedColumn" FROM the_table;. If, however, I try doing the same in the WHERE clause, then I get an error.
For example, SELECT * FROM the_table WHERE "myCamelCasedColumn" = "hello"; gives me the error column "hello" does not exist.
How can I get around this? If I don't surround the column in double quotation marks then it will just complain that column mycamelcasedcolumn does not exist.
In SQL string literals are enclosed in single quotes, not double quotes.
SELECT *
FROM the_table
WHERE "myCamelCasedColumn" = 'hello';
See the manual for details:
http://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
The manual also explains why "myCamelCasedColumn" is something different in SQL than myCamelCasedColumn
In general you should stay away from quoted identifiers. They are much more trouble than they are worth it. If you never use double quotes everything is a lot easier.
The problem is you use double quote for strin literal "hello". Should be 'hello'. Double quotes is reserved for identifiers.
I asked similar question here for: hstore value with space. And get solved by user: Clodoaldo Neto. Now I have come across next case with string containing single quote.
SELECT 'k=>"name", v=>"St. Xavier's Academy"'::hstore;
I tried it by using dollar-quoted string constant by reading http://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS
SELECT 'k=>"name", v=>$$St. Xavier's Academy$$'::hstore;
But I couldn't get it right.
How to make postgresql hstore using strings containing single quote?
It seems like there are more such exceptions possible for this query. How to address them all at once?
You can escape the embedded single quote that same way you'd escape any other single quote inside a string literal: double it.
SELECT 'k=>"name", v=>"St. Xavier''s Academy"'::hstore;
-- ------------------------------^^
Alternatively, you could dollar quote the whole string:
SELECT $$k=>"name", v=>"St. Xavier's Academy"$$::hstore;
Whatever interface you're using to talk to PostgreSQL should be taking care of these quoting and escaping issues. If you're using manual string wrangling to build your SQL then you should be using your driver's quoting and placeholder methods.
hstore's internal parsing understands double quotes around keys:
Double-quote keys and values that include whitespace, commas, =s or >s.
Dollar quoting is, as you noted, for SQL string literals, hstore's parser doesn't know what they mean.
I need to update a record, which contains literal percent signs, using PostgreSQL in Railo. The query looks like
<cfquery>
update foo set bar = 'string with % in it %'
</cfQuery>
It throws error as ColdFusion normally interprets it as a wildcard character. I can escape it using the following query.
<cfquery>
update foo set bar = 'string with escaped \% in it \%'
</cfQuery>
However, the record now contains "\%" in the database and will be displayed on the page as "\%".
I found a documentation with an example of escaping percent sign in a SELECT. But it does not work for me: syntax error at or near "ESCAPE".
SELECT emp_discount
FROM Benefits
WHERE emp_discount LIKE '10\%'
ESCAPE '\';
Is there a better to achieve the same goal? The underlining database is PostgreSQL. Thanks!
Queryparameters escape special characters. Yet another reason to use them.