Mysql substring string and attach chars such as ... to result command - mysql

My subject field is (maybe) bigger than 100 characters. I want to use LENGTH if subject length is bigger that 100 char in below mysql command and attach ... to end of SUBSTR subject.
SELECT id ,
IF LENGTH(`subject`) <=100 then SUBSTR( `subject`, 1, 100 ) AS subject
ELSE `subject`
END IF
FROM `contents`


You might be looking for CONCAT function in MySQL.
SELECT id ,
CASE WHEN LENGTH(`subject`) >=100 then CONCAT(SUBSTR( `subject`, 1, 100 ),'...')
ELSE `subject`
END AS `subject`
FROM `contents`
Sample fiddle
Have a look here as well.


Rather another simpler way could be you can fetch the subject using your simple mysql query. and can display your subject this way!!
For ex: $subject = substr($data['subject'], 1, 100)

Related

Why CONCAT does not insert text for the first time into mySQL table?

I am using UPDATE to insert simple text into a table where the field is MEDIUMTEXT (nullable field).
It is strange that it does not work when the field is null initially. If I manually enter at least a one character/space, then it's working.
I want to append the new text into existing text in the field.
UPDATE pen SET
PEN_STATUS = #PenStat,
PEN_STATUS_CHANGE_REASON = CONCAT(PEN_STATUS_CHANGE_REASON,'\n',ChangeDate,':',EmployeeID,':',ChangeReason)
WHERE PEN_ID = PenID;
Why is this?

CONCAT does not handle NULL values. As explained in the MySQL manual:
CONCAT() returns NULL if any argument is NULL.
You want to use COALESCE to handle that use case, like :
UPDATE pen SET
PEN_STATUS = #PenStat,
PEN_STATUS_CHANGE_REASON = CONCAT(
COALESCE(PEN_STATUS_CHANGE_REASON, ''),
'\n',
ChangeDate,
':',
EmployeeID,
':',
ChangeReason
)
WHERE PEN_ID = PenID;

Presumably, because something is NULL. Try using CONCAT_WS() instead:
UPDATE pen
SET PEN_STATUS = #PenStat,
PEN_STATUS_CHANGE_REASON = CONCAT_WS('\n',
PEN_STATUS_CHANGE_REASON,
CONCAT_WS(':', ChangeDate, EmployeeID, ChangeReason
)
)
WHERE PEN_ID = PenID;
CONCAT_WS() ignores NULL arguments. Plus, the separator only needs to be listed once.

Teradata Masking - Retain all chararcters at position 1,4,8,12,16 .... in a string and mask remaining characters with 'X'

I have a requirement where I need to mask all but characters in position 1,4,8,12,16.. for a variable length string with 'X'
For example:
Input string - 'John Doe'
Output String - 'JXXn xxE'
SPACE between the two strings must be retained.
Kindly help or reach out for more details if required.

I think maybe an external function would be best here, but if that's too much to bite off, you can get crafty with strtok_split_to_table, xml_agg and regexp_replace to rip the string apart, replace out characters using your criteria, and stitch it back together:
WITH cte AS (SELECT REGEXP_REPLACE('this is a test of this functionality', '(.)', '\1,') AS fullname FROM Sys_Calendar.calendar WHERE calendar_date = CURRENT_DATE)
SELECT
REGEXP_REPLACE(REGEXP_REPLACE((XMLAGG(tokenout ORDER BY tokennum) (VARCHAR(200))), '(.) (.)', '\1\2') , '(.) (.)', '\1\2')
FROM
(
SELECT
tokennum,
outkey,
CASE WHEN tokennum = 1 OR tokennum mod 4 = 0 OR token = ' ' THEN token ELSE 'X' END AS tokenout
FROM TABLE (strtok_split_to_table(cte.fullname, cte.fullname, ',')
RETURNS (outkey VARCHAR(200), tokennum integer, token VARCHAR(200) CHARACTER SET UNICODE)) AS d
) stringshred
GROUP BY outkey
This won't be fast on a large data set, but it might suffice depending on how much data you have to process.
Breaking this down:
WITH cte AS (SELECT REGEXP_REPLACE('this is a test of this functionality', '(.)', '\1,') AS fullname FROM Sys_Calendar.calendar WHERE calendar_date = CURRENT_DATE)
This CTE is just adding a comma between every character of our incoming string using that regexp_replace function. Your name will come out like J,o,h,n, ,D,o,e. You can ignore the sys_calendar part, I just put that in so it would spit out exactly 1 record for testing.
SELECT
tokennum,
outkey,
CASE WHEN tokennum = 1 OR tokennum mod 4 = 0 OR token = ' ' THEN token ELSE 'X' END AS tokenout
FROM TABLE (strtok_split_to_table(cte.fullname, cte.fullname, ',')
RETURNS (outkey VARCHAR(200), tokennum integer, token VARCHAR(200) CHARACTER SET UNICODE)) AS d
This subquery is the important bit. Here we create a record for every character in your incoming name. strtok_split_to_table is doing the work here splitting that incoming name by comma (which we added in the CTE)
The Case statement just runs your criteria swapping out 'X' in the correct positions (record 1, or a multiple of 4, and not a space).
SELECT
REGEXP_REPLACE(REGEXP_REPLACE((XMLAGG(tokenout ORDER BY tokennum) (VARCHAR(200))), '(.) (.)', '\1\2') , '(.) (.)', '\1\2')
Finally we use XMLAGG to combine the many records back into one string in a single record. Because XMLAGG adds a space in between each character we have to hit it a couple of times with regexp_replace to flip those spaces back to nothing.
So... it's ugly, but it does the job.
The code above spits out:
tXXs XX X XeXX oX XhXX fXXXtXXXaXXXy

I couldn't think of a solution, but then #JNevill inspired me with his idea to add a comma to each character :-)
SELECT
RegExp_Replace(
RegExp_Replace(
RegExp_Replace(inputString, '(.)(.)?(.)?(.)?', '(\1(\2[\3(\4', 2)
,'(\([^ ])', 'X')
,'(\(|\[)')
,'this is a test of this functionality' AS inputString
tXXs XX X XeXX oX XhXX fXXXtXXXaXXXy
The 1st RegExp_Replace starts at the 2nd character (keep the 1st character as-is) and processes groups of (up to) 4 characters adding either a ( (characters #1,#2,#4, to be replaced by X unless it's a space) or [ (character #3, no replacement), which results in :
t(h(i[s( (i(s[ (a( (t[e(s(t( [o(f( (t[h(i(s( [f(u(n(c[t(i(o(n[a(l(i(t[y(
Of course this assumes that both characters don't exists in your input data, otherwise you have to choose different ones.
The 2nd RegExp_Replace replaces the ( and the following character with X unless it's a space, which results in:
tXX[s( XX[ X( X[eXX( [oX( X[hXX( [fXXX[tXXX[aXXX[y(
Now there are some (& [ left which are removed by the 3rd RegExp_Replace.
As I still consider me as a beginner in Regular Expressions, there will be better solutions :-)
Edit:
In older Teradata versions not all parameters were optional, then you might have to add values for those:
RegExp_Replace(
RegExp_Replace(
RegExp_Replace(inputString, '(.)(.)?(.)?(.)?', '(\1(\2[\3(\4', 2, 0 'c')
,'(\([^ ])', 'X', 1, 0 'c')
,'(\(|\[)', '', 1, 0 'c')

MySQL Correct title/proper case for more than one string in a field

I have a database which has a field titled 'address1'. If there is only 1 string in this field for a record, I am able to correct the case from eg 'PAULSTOWN' to 'Paulstown', or 'bishopslough' to 'Bishopslough'.
I have done this by creating a function:
CREATE FUNCTION init_cap (s VARCHAR(255))
RETURNS VARCHAR(255) DETERMINISTIC
RETURN CONCAT( UPPER( SUBSTRING( s, 1, 1 ) ) , LOWER( SUBSTRING( s FROM 2 ) ) );
Then using:
UPDATE customer SET address1 = init_cap(address1);
To correct records.
However, this does not fully correct records that contain more than one string, eg 'dalesfort road' will only be corrected to 'Dalesfort road' and not 'Dalesfort Road'. There are also some entries with more than 2 strings.
How could I change the above function to cater for 2 or more strings? Also is that function declared correctly, or should I be using begin and end sections?

It's ok I found the answer at artfulsoftware.com
Now I just need to analyse the code and learn how it works!

Increase Alphanumeric VARCHAR Entry by Value 1?

On an old project because of not thought through design I have a column which actually should be set to auto_increment, though it cannot be because it are alphanumeric entries as follows:
c01
c02
c03
(c99 would continue to c100 and more), the letter happened in the past and it would require to overhaul the system to take it out, thus I rather prefer this workaround.
Now I need a way to imitate the auto_increment functionality with the SQL statement myself, my own attempt has gotten as far as the following:
INSERT INTO tags (tag_id, tag_name, tag_description, added_by_user_id, creation_date, last_edited) VALUES (SELECT(MAX(tag_id)+1),
'Love', 'All about love', 7, now(), 0);
This one does not work as is, though the idea was to select the highest entry in the column "tag_id" and then simply increase it by the value 1.
Any ideas how to accomplish this?
By the way I am also not sure if you simply can increase an alphanumeric entry through this way, though I know it can be done, I just don't know how.

If you want to safely get the largest integer value of a tag id of the form c##.., you could use the following expression:
max( convert( substring(tag_id, 2) , unsigned integer) )
^^^ largest ^^^^^^^^^ after 'c' ^^^^^^^^^^^^^^^^ convert to positive number
Then your insert statement would look something like this:
set #newid = convert(
(select
max(convert( (substring(tag_id, 2)) , unsigned integer))+1
from tags), char(10)
);
set #newid = if(length(#newid) = 1, concat('0', #newid), #newid);
set #newid = concat('c', #newid);
INSERT INTO tags (tag_id, tag_name, tag_description, added_by_user_id,
creation_date, last_edited)
VALUES (#newid, 'Love', 'All about love', 7, now(), '2012-04-15');
Demo: http://www.sqlfiddle.com/#!2/0bd9f/1

this will increase from c01 to c02 to c03 ... to c99 to c100 to c101 ... to c999 to c1000 etc.
set #nextID = (SELECT CONCAT(SUBSTRING(`tag_id`, 1, 1), IF(CHAR_LENGTH(CAST(SUBSTRING(`tag_id`, 2)
AS UNSIGNED)) < 2, LPAD(CAST(CAST(SUBSTRING(`tag_id`, 2) AS UNSIGNED) + 1 AS CHAR), 2,
'0'), CAST(CAST(SUBSTRING(`tag_id`, 2) AS UNSIGNED) + 1 AS CHAR))) FROM `tags` ORDER BY
`tag_id` DESC LIMIT 1);
INSERT INTO tags (tag_id, tag_name, tag_description, added_by_user_id,
creation_date, last_edited) VALUES (#nextID, 'Love', 'All about love', 7, NOW(), null);

MySQL GROUP_CONCAT escaping

(NOTE: This question is not about escaping queries, it's about escaping results)
I'm using GROUP_CONCAT to combine multiple rows into a comma delimited list. For example, assume I have the two (example) tables:
CREATE TABLE IF NOT EXISTS `Comment` (
`id` int(11) unsigned NOT NULL auto_increment,
`post_id` int(11) unsigned NOT NULL,
`name` varchar(255) collate utf8_unicode_ci NOT NULL,
`comment` varchar(255) collate utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
KEY `post_id` (`post_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=6 ;
INSERT INTO `Comment` (`id`, `post_id`, `name`, `comment`) VALUES
(1, 1, 'bill', 'some comment'),
(2, 1, 'john', 'another comment'),
(3, 2, 'bill', 'blah'),
(4, 3, 'john', 'asdf'),
(5, 4, 'x', 'asdf');
CREATE TABLE IF NOT EXISTS `Post` (
`id` int(11) NOT NULL auto_increment,
`title` varchar(255) collate utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=7 ;
INSERT INTO `Post` (`id`, `title`) VALUES
(1, 'first post'),
(2, 'second post'),
(3, 'third post'),
(4, 'fourth post'),
(5, 'fifth post'),
(6, 'sixth post');
And I want to list all posts along with a list of each username who commented on the post:
SELECT
Post.id as post_id, Post.title as title, GROUP_CONCAT(name)
FROM Post
LEFT JOIN Comment on Comment.post_id = Post.id
GROUP BY Post.id
gives me:
id title GROUP_CONCAT( name )
1 first post bill,john
2 second post bill
3 third post john
4 fourth post x
5 fifth post NULL
6 sixth post NULL
This works great, except that if a username contains a comma it will ruin the list of users. Does MySQL have a function that will let me escape these characters? (Please assume usernames can contain any characters, since this is only an example schema)

Actually, there are ascii control characters specifically designed for separating database fields and records:
0x1F (31): unit (fields) separator
0x1E (30): record separator
0x1D (29): group separator
Read more: about ascii characters
You will never have them in usernames and most probably never in any other non-binary data in your database so they can be used safely:
GROUP_CONCAT(foo SEPARATOR 0x1D)
Then split by CHAR(0x1D) in whatever client language you want.

If there's some other character that's illegal in usernames, you can specify a different separator character using a little-known syntax:
...GROUP_CONCAT(name SEPARATOR '|')...
... You want to allow pipes? or any character?
Escape the separator character, perhaps with backslash, but before doing that escape backslashes themselves:
group_concat(replace(replace(name, '\\', '\\\\'), '|', '\\|') SEPARATOR '|')
This will:
escape any backslashes with another backslash
escape the separator character with a backslash
concatenate the results with the separator character
To get the unescaped results, do the same thing in the reverse order:
split the results by the separator character where not preceded by a backslash. Actually, it's a little tricky, you want to split it where it isn't preceded by an odd number of blackslashes. This regex will match that:
(?<!\\)(?:\\\\)*\|
replace all escaped separator chars with literals, i.e. replace \| with |
replace all double backslashes with singe backslashes, e.g. replace \\ with \

REPLACE()
Example:
... GROUP_CONCAT(REPLACE(name, ',', '\\,'))
Note you have to use a double-backslash (if you escape the comma with backslash) because backslash itself is magic, and \, becomes simply ,.

I'd suggest GROUP_CONCAT(name SEPARATOR '\n'), since \n usually does not occur. This might be a little simpler, since you don't need to escape anything, but could lead to unexpected problems. The encodeing/regexp decoding stuff as proposed by nick is of course nice too.

If you're going to be doing the decoding in your application, maybe just use hex:
SELECT GROUP_CONCAT(HEX(foo)) ...
or you could also put the length in them:
SELECT GROUP_CONCAT(CONCAT(LENGTH(foo), ':', foo)) ...
Not that I tested either :-D

what nick said really, with an enhancement - the separator can be more than one character too.
I've often used
GROUP_CONCAT(name SEPARATOR '"|"')
Chances of a username containing "|" are fairly low i'd say.

You're getting into that gray area where it might be better to postprocess this outside the world of SQL.
At least that's what I'd do: I'd just ORDER BY instead of GROUP BY, and loop through the results to handle the grouping as a filter done in the client language:
Start by initializing last_id to NULL
Fetch the next row of the resultset (if there aren't more rows go to step 6)
If the id of the row is different than last_id start a new output row:
a. if last_id isn't NULL then output the grouped row
b. set the new grouped row = the input row, but store the name as a single element array
c. set last_id to the value of the current ID
Otherwise (id is the same as last_id) append the row name onto the existing grouped row.
Go back to step 2
Otherwise you have finished; if the last_id isn't NULL then output the existing group row.
Then your output ends up including names organized as an array and can decide how you want to handle/escape/format them then.
What language/system are you using? PHP? Perl? Java?

Jason S: This is exactly the issue I'm dealing with. I'm using an PHP MVC framework and was processing the results like you describe (multiple rows per result and code to group the results together). However, I've been working on two functions for my models to implement. One returns a list of all necessary fields needed to recreate the object and the other is a function that given a row with the fields from the first function, instantiate a new object. This lets me request a row from the database and easily turn it back into the object without knowing the internals of the data needed by the model. This doesn't work quite as well when multiple rows represent one object, so I was trying to use GROUP_CONCAT to get around that problem.

Right now I'm allowing any character. I realize a pipe would be unlikely to show up, but I'd like to allow it.
How about a control character, which you should be stripping out of application input anyway? I doubt you need eg. a tab or a newline in a name field.

Just to expand on some of the answers, I implemented #derobert 's second suggestion in PHP and it works well. Given MySQL such as:
GROUP_CONCAT(CONCAT(LENGTH(field), ':', field) SEPARATOR '') AS fields
I used the following function to split it:
function concat_split( $str ) {
// Need to guard against PHP's stupid multibyte string function overloading.
static $mb_overload_string = null;
if ( null === $mb_overload_string ) {
$mb_overload_string = defined( 'MB_OVERLOAD_STRING' )
&& ( ini_get( 'mbstring.func_overload' ) & MB_OVERLOAD_STRING );
}
if ( $mb_overload_string ) {
$mb_internal_encoding = mb_internal_encoding();
mb_internal_encoding( '8bit' );
}
$ret = array();
for ( $offset = 0; $colon = strpos( $str, ':', $offset ); $offset = $colon + 1 + $len ) {
$len = intval( substr( $str, $offset, $colon ) );
$ret[] = substr( $str, $colon + 1, $len );
}
if ( $mb_overload_string ) {
mb_internal_encoding( $mb_internal_encoding );
}
return $ret;
}
I also initially implemented #ʞɔıu 's suggestion, using one of #Lemon Juice 's separators. It worked fine but apart from its complication it was slower, the main problem being that PCRE only allows fixed length lookbehind so using the suggested regex to split requires capturing the delimiters, otherwise doubled backslashes at the end of strings will be lost. So given MySQL such as (note 4 PHP backslashes => 2 MySQL backslashes => 1 real backslash):
GROUP_CONCAT(REPLACE(REPLACE(field, '\\\\', '\\\\\\\\'),
CHAR(31), CONCAT('\\\\', CHAR(31))) SEPARATOR 0x1f) AS fields
the split function was:
function concat_split( $str ) {
$ret = array();
// 4 PHP backslashes => 2 PCRE backslashes => 1 real backslash.
$strs = preg_split( '/(?<!\\\\)((?:\\\\\\\\)*+\x1f)/', $str, -1, PREG_SPLIT_DELIM_CAPTURE );
// Need to add back any captured double backslashes.
for ( $i = 0, $cnt = count( $strs ); $i < $cnt; $i += 2 ) {
$ret[] = isset( $strs[ $i + 1 ] ) ? ( $strs[ $i ] . substr( $strs[ $i + 1 ], 0, -1 ) ) : $strs[ $i ];
}
return str_replace( array( "\\\x1f", "\\\\" ), array( "\x1f", "\\" ), $ret );
}