I have a very long comment I want to add to a Postgres table.
Since I do not want a very long single line as a comment I want to split it into several lines.
Is this possible? \n does not work since Postgres does not use the backslash as an escape character.
Just write a multi-line string:
COMMENT ON TABLE foo IS 'This
comment
is stored
in multiple lines';
You can also embed \n escape sequences in “extended” string constants that start with E:
COMMENT ON TABLE foo IS E'A comment\nwith three\nlines.';
You can use automatic concatenation of adjacent string literals together with E'\n' escape sequences for linebreaks:
COMMENT ON TABLE foo IS E''
'This comment is stored in multiple lines. But only some'
'end with linebreaks like this one.\n'
'You can even create empty lines to simulate paragraphs:'
'\n\n'
'This would be the second paragraph, then.';
Details:
Note the initial E'' at the end of the first line. This is essential to make all the adjacent string literals that follow it use the extended string literal syntax, providing us with the option to write \n for a linebreak. Of course, that E could also be placed into the second line instead, at the start of the real string: E'This comment …'. Me putting it into the first line is just source code aesthetics … character alignment and stuff.
I consider this solution slightly better than multi-line strings (proposed in another answer here) because it allows to fit the comment into the typical line width limit and the indentation requirements of source files. Useful when you keep your SQL in well-formatted files under version control, that is, treating it just as any other source code. When including indentation into multi-line strings, on the other hand, this results in lots of additional whitespace in the live table comment.
Note for OP: When you say "I do not want a very long single line as a comment", it is not clear if you don't want that long line in your .sql source code file, or if you don't want it in the table comment of the live table, such as when seen in a database admin tool. It does not really matter, as this solution gives you tools for both purposes: use adjacent string literals to fit your line into the source code file, without affecting line breaks in the live table comment; and use \n to create line breaks and empty lines in the live table comment.
Related
How do I prevent newlines in the readme.md files (GitHub)?
We can always write the whole thing in one line to prevent it. But is there an exclusive tag/option to prevent the same, especially for tags that create newlines (headings) like span in html?
Doesn't a space followed by a backslash do the concatenation you want? It does for me. That way I can break a paragraph into one sentence per line.
When viewed, any .csv file committed to a GitHub repository automatically renders as an interactive table, complete with headers and row numbering. By default, the first row is your header row. The tables were supposed to look nice as below:
However, there's an error happening in my tabular data, and despite indicating the error, I can't fix it:
I'm using a .csv file with a semicolon separator. Does anyone have an idea of what's happening?
According to the docs, Github can only do its lay-out thing with .csv (comma-separated) and .tsv (tab-separated) files.
Using a semicolon as a separator isn't supported, at least not officially, and a spurious comma in a semicolon-separated file could well throw the algorithm off.
You could try replacing all semicolons with tabs and see how you fare.
If that doesn't work, try using commas as separators and enclose all text table cell data with quotes, like:
"Liver fibrosis, sclerosis, and cirrhosis","c370800","102922","Cystic fibrosis related cirrhosis","Diagnosis of liver fibrosis, sclerosis, and cirrhosis"
Note: no spaces after the commas. Also, if you have quotes in the text fields, you will have to escape those to "" (two quotes), or the algorithm will get confused.
You may get away with using quotes only for the offending text data, but that could well be more difficult to generate than just putting the quotes around all fields.
I'm working to build an import tool that utilizes a quoted CSV file. However, several of the fields in the CSV file are reported as such:
"=""38000"""
Where 38000 is the data I need. The data integration software I use (Talend 6.11) already strips the leading and trailing double quotes for me (so, "38000" becomes 38000), but I can't find a way to get rid of those others.
So, essentially, I need "=""38000""" to become "38000" where the leading "=" is removed and the trailing "" is removed.
Is there a TRIM function that can accomplish this for me? Perhaps there is a method in Talend that can do this?
As the other answer stated, you could do that operation in SQL. Or, you could do it in Java, Groovy, etc, within Talend. However, if there is an existing Talend component which does the job, my preference is to use it. That leads to faster development, potentially less testing, and easier maintenance. Having said that, it is important to review all the components which are available, so you know what's available to you.
You can use the Talend component tReplace, to inspect each of the input columns you want to trim of quotes and equal signs. A single tReplace component can do search and replace operations on multiple input columns. If all the of the replaces are related to each other, I would keep them within a single tReplace. When it gets to the point of doing unrelated replacements, I might place those within a new tReplace so that logical operations are organized and grouped together.
tReplace
For a given Input Column
search for "=", replace with ""
search for "\"", replace with ""
Something like that:
SELECT format( '"%s"', trim( both '"=' from '"=""38000"""' ) );
-[ RECORD 1 ]---
format | "38000"
1st: trim() function removes all " and = chars. Result is simply 38000
2nd: with format can add double quote back to get wishful end result
Alternatively, can use regexp and other Postgres string functions.
See more:
https://www.postgresql.org/docs/current/static/functions-string.html
I want to search a file for a specific string and then place a comment at the beginning of that string. But I need an answer that avoids regex, global changes, and all the other fancy stuff.
I wrote this line:
sed -i.bak '/PermitRootLogin no/# PermitRootLogin no/' ./sshd_config
but I get an error:
sed: -e expression #1, char 21: comments don't accept any addresses
I assume the issue is that I need to escape the # character, but I'm not finding any resources on how to do that, or even mentioning it. I've tried various combinations of putting ^ or \ or \^ in front of the # but I'm jut not getting it right.
Please note I am intentionally repeating the text to be replaced. I would like the most simple possible solution to this question: how to replace "XYX" with "# XYZ" in the most obvious possible way.
As indicated in the comments by #mlt , you could try adding an s at the beginning your sed command. Straight from his comment:
s/PermitRootLogin....
I see that you said you're intentionally repeating the test to be replaced. If by that you mean, you want it to be the same, maybe consider grouping your matched text. I understand you may have meant that you just want it hand typed. Anyway, here is how to match the grouped text and add the comment character:
s/(PermitRootLogin)/# \1/
The parens indicated that the matched text should be consider a group, the \1 indicates that you want to put that matched group there.
I hope this was helpful. Happy coding! Leave a comment if you have any questions.
Imagine I have a file that has the following type of line:
FIXED_DATA1 VARIABLE_DATA FIXED_DATA2
I want to change the fixed data and leave the variable data as is. For various reasons, using two sed operations to replace the fixed data will not work. For instance, the fixed fields might be double-quotes, and the line has other areas containing them, thus really the regex is written to match a pattern in the variable data and the fixed data.
If I'm bent on using sed, is there a way to change both fixed data fields at once while leaving the variable field unchanged?
Thanks.
You need to partition the line into the three pieces, replace the outer two and leave the middle alone:
sed 's/^FIX1 \(.*\) FIX2$/New \1 End/'
You can make the beginning and end matches more complex as needed.