I would like to use goto in MySQL stored function.
How can I use?
Sample code is:
if (action = 'D') then
if (rowcount > 0) then
DELETE FROM datatable WHERE id = 2;
else
SET p=CONCAT('Can not delete',#b);
goto ret_label;
end if;
end if;
Label: ret_label;
return 0;
There are GOTO cases which can't be implemented in MySQL, like jumping backwards in code (and a good thing, too).
But for something like your example where you want to jump out of everything to a final series of statements, you can create a BEGIN / END block surrounding the code to jump out of:
aBlock:BEGIN
if (action = 'D') then
if (rowcount > 0) then
DELETE FROM datatable WHERE id = 2;
else
SET p=CONCAT('Can not delete',#b);
LEAVE aBlock;
end if;
end if;
END aBlock;
return 0;
Since your code is just some nested IFs, the construct is unnecessary in the given code. But it makes more sense for LOOP/WHILE/REPEAT to avoid multiple RETURN statements from inside a loop and to consolidate final processing (a little like TRY / FINALLY).
There is no GOTO in MySQL Stored Procs. You can refer to this post:
MySQL :: Re: Goto Statement
Related
I have a table where each row consist of an attribute which consist of html data with like this.
<div className="single_line"><p>New note example</p></div>
I need to omit the html tags and extract only the data inside the tags using sql query. Any idea on how to achieve this?. I tried out different regex but they didnt work.
There are 2 solutions based on mysql version.
If you are using MySQL 8.0 then you can use REGEXP_REPLACE() directly inside the select statement.
SELECT REGEXP_REPLACE('<div><p>New note example</p></div>', '(<[^>]*>)|( )', '');
If you are using MySQL 5.7 then you have to create a user define function in database to strip html tags.
DROP FUNCTION IF EXISTS fn_strip_html_tags;
CREATE FUNCTION fn_strip_html_tags( html_text TEXT ) RETURNS TEXT
BEGIN
DECLARE start,end INT DEFAULT 1;
DECLARE text_without_nbsp TEXT;
LOOP
SET start = LOCATE("<", html_text, start);
IF (!start) THEN RETURN html_text; END IF;
SET end = LOCATE(">", html_text, start);
IF (!end) THEN SET end = start; END IF;
SET text_without_nbsp = REPLACE(html_text, " ", " ");
SET html_text = INSERT(text_without_nbsp, start, end - start + 1, "");
END LOOP;
END
For example
SELECT fn_strip_html_tags('<div><p>New note example</p></div>');
When the below function is executed, I get the following error message "Output argument "max_idx" (and maybe others) not assigned during call to "find_node"."
I think the problem is in the fact that some output is produced after recursive loop. How can I solve this?
function max_idx = find_node(wt)
persistent all_idx_max;
node_degree=sum(wt,2);
maxval = max(node_degree);
all_nodes_with_max_val = ismember(node_degree,maxval);
idx_max = find(all_nodes_with_max_val);
if isempty(all_idx_max)
all_idx_max=1:8;
end
if size(idx_max,1)==3
max_idx=all_idx_max(idx_max(1))
elseif size(idx_max,1)>1
all_idx_max=idx_max;
find_node(wt(idx_max,idx_max)); <--problem happens in this path
else
max_idx=all_idx_max(idx_max)
end
I forgot to add output to the recursive part
function max_idx = find_node(wt)
persistent all_idx_max;
node_degree=sum(wt,2);
maxval = max(node_degree);
all_nodes_with_max_val = ismember(node_degree,maxval);
idx_max = find(all_nodes_with_max_val);
if isempty(all_idx_max)
all_idx_max=1:8;
end
if size(idx_max,1)==3
max_idx=all_idx_max(idx_max(1))
elseif size(idx_max,1)>1
all_idx_max=idx_max;
***max_idx =*** find_node(wt(idx_max,idx_max)); <--problem happens in this path
else
max_idx=all_idx_max(idx_max)
end
Preface:
I've done quite a bit of (re)searching on this, and found the following SO post/answer: https://stackoverflow.com/a/5361490/6095216 which was pretty close to what I'm looking for. The same code, but with somewhat more helpful comments, appears here: http://thenoyes.com/littlenoise/?p=136 .
Problem Description:
I need to split 1 column of MySQL TEXT data into multiple columns, where the original data has this format (N <= 7):
{"field1":"value1","field2":"value2",...,"fieldN":"valueN"}
As you might guess, I only need to extract the values, putting each one into a separate (predefined) column. The problem is that the number and order of the fields is not guaranteed to be the same for all records. Thus, solutions using SUBSTR/LOCATE, etc. don't work, and I need to use regular expressions. Another restriction is that 3rd party libraries such as LIB_MYSQLUDF_PREG (suggested in the answer from my 1st link above) cannot be used.
Solution/Progress so far:
I've modified the code from the above links such that it returns the first/shortest match, left-to-right; otherwise, NULL is returned. I also refactored it a bit and made the identifiers more reader/maintainer-friendly :)
Here's my version:
CREATE FUNCTION REGEXP_EXTRACT_SHORTEST(string TEXT, exp TEXT)
RETURNS TEXT DETERMINISTIC
BEGIN
DECLARE adjustStart, adjustEnd BOOLEAN DEFAULT TRUE;
DECLARE startInd INT DEFAULT 1;
DECLARE endInd, strLen INT;
DECLARE candidate TEXT;
IF string NOT REGEXP exp THEN
RETURN NULL;
END IF;
IF LEFT(exp, 1) = '^' THEN
SET adjustStart = FALSE;
ELSE
SET exp = CONCAT('^', exp);
END IF;
IF RIGHT(exp, 1) = '$' THEN
SET adjustEnd = FALSE;
ELSE
SET exp = CONCAT(exp, '$');
END IF;
SET strLen = LENGTH(string);
StartIndLoop: WHILE (startInd <= strLen) DO
IF adjustEnd THEN
SET endInd = startInd;
ELSE
SET endInd = strLen;
END IF;
EndIndLoop: WHILE (endInd <= strLen) DO
SET candidate = SUBSTRING(string FROM startInd FOR (endInd - startInd + 1));
IF candidate REGEXP exp THEN
RETURN candidate;
END IF;
IF adjustEnd THEN
SET endInd = endInd + 1;
ELSE
LEAVE EndIndLoop;
END IF;
END WHILE EndIndLoop;
IF adjustStart THEN
SET startInd = startInd + 1;
ELSE
LEAVE StartIndLoop;
END IF;
END WHILE StartIndLoop;
RETURN NULL;
END;
I then added a helper function to avoid having to repeat the regex pattern, which, as you can see from above, is the same for all the fields. Here is that function (I left my attempt to use a lookbehind - unsupported in MySQL - as a comment):
CREATE FUNCTION GET_MY_FLD_VAL(inputStr TEXT, fldName TEXT)
RETURNS TEXT DETERMINISTIC
BEGIN
DECLARE valPattern TEXT DEFAULT '"[^"]+"'; /* MySQL doesn't support lookaround :( '(?<=^.{1})"[^"]+"'*/
DECLARE fldNamePat TEXT DEFAULT CONCAT('"', fldName, '":');
DECLARE discardLen INT UNSIGNED DEFAULT LENGTH(fldNamePat) + 2;
DECLARE matchResult TEXT DEFAULT REGEXP_EXTRACT_SHORTEST(inputStr, CONCAT(fldNamePat, valPattern));
RETURN SUBSTRING(matchResult FROM discardLen FOR LENGTH(matchResult) - discardLen);
END;
Currently, all I'm trying to do is a simple SELECT query using the above code. It works correctly, BUT IT. IS. SLOOOOOOOW... There are only 7 fields/columns to split into, max (not all records have all 7)! Limited to 20 records, it takes about 3 minutes - and I have about 40,000 records total (not very much for a database, right?!) :)
And so, finally, we get to the actual question: [how] can the above algorithm/code (pretty much a brute search at this point) be improved SIGNIFICANTLY performance-wise, such that it can be run on the actual database in a reasonable amount of time? I started looking into the major known pattern-matching algorithms, but quickly got lost trying to figure out what would be appropriate here, in large part due to the number of available options and their respective restrictions, conditions for use, etc. Plus, it seems like implementing one of these in SQL just to see if it would help, might be a lot of work.
Note: this is my first post ever(!), so please let me know (nicely) if something is not clear, etc. and I will do my best to fix it. Thanks in advance.
I was able to solve this by parsing the JSON, as suggested by tadman and Matt Raines above. Being new to the concept of JSON, I just didn't realize it could be done this way at all...a little embarrassing, but lesson learned!
Anyway, I used the get_option function in the common_schema framework: https://code.google.com/archive/p/common-schema/ (found through this post, which also demonstrates how to use the function: Parse JSON in MySQL ). As a result, my INSERT query took about 15 minutes to run, vs the 30+ hours it would've taken with the REGEXP solution. Thanks, and until next time! :)
Don't do it in SQL; do it in PHP or some other language that has builtin tools for parsing JSON.
I want to use goto statement in Mysql stored procedure in such manner that I execute my cursor whenever condition become true once again.
This is a sample code only, I just looking for goto statement
BLOCK_BACKLOG:begin
declare backlgId, oldCOR, oldATR,oldCourse,oldATR,isFormFilled,nextParentId int;
declare backlogNoMoreRow boolean default false;
Label : TestLineStart
declare backlogCur cursor for select bcklg.id,cor.id,atr.id,cr.id,atr.obtainedMarks,atr.isFormFilled,atr.parentRegistration_id
from train bcklg,bus cor,fliet atr,fair co,distance cr
where bcklg.courseofferingregistration_id=cor.id and cor.academictermregistration_id=atr.id and cor.courseoffering_id=co.id and co.course_id=cr.id
and bcklg.isDeleted is false and atr.id=parentId;
declare continue handler for not found set backlogNoMoreRow=true;
open backlogCur;
LOOP_BACKLOG: loop
fetch backlogCur into backlgId, oldCOR, oldATR,oldCourse,oldATRMarks,isFormFilled,nextParentId;
if backlogNoMoreRow then
close backlogCur;
leave LOOP_BACKLOG;
end if;
if isFormFilled==0 then
parentId=nextParentId;
GOTO TestLineStart;
end if;
You can use a LOOP on the outer block based on the value for variable isFormFilled.
Following change may help you.
-- Label : TestLineStart
TestLineStart: LOOP
-- other part of your SP as it is
and make following change:
if isFormFilled==0 then
parentId=nextParentId;
-- GOTO TestLineStart;
else
leave TestLineStart;
end if;
You have to close all loop statements properly.
I'm trying to write a sql statement that will insert data given a few setup variables. I don't want to create a stored procedure, as it's not something I'll be dealing with anywhere except as an administrator and I don't want the stored procedure hanging around. I just want a statement that works. Here's what I have so far:
SET #app = 7;
SET #time = UNIX_TIMESTAMP(NOW());
SET #maxValue = 100;
SET #decrement = 10;
SET #category = 1;
SET #minSubcategory = 0;
SET #maxSubcategory = 19;
SET #subcategory = #minSubcategory;
subcat_loop: LOOP
SET #idx = 0;
insert_loop: LOOP
SET #id = CONCAT('TempId', #idx+1);
SELECT #name:=username FROM user WHERE id = #id;
SET #value = #maxValue - #decrement * #idx;
INSERT INTO data (userId, username, app, category, subcategory, value, date) VALUES
(#id, #name, #app, #category, #subcategory, #value, #time);
SET #idx = #idx+ 1;
IF #idx > 10 THEN
LEAVE insert_loop;
END IF;
END LOOP insert_loop;
SET #subcategory = #subcategory + 1;
IF #subcategory > #maxSubcategory THEN
LEAVE subcat_loop;
END IF;
END LOOP subcat_loop;
But it doesn't like the SET #idx = 0 inside the loop for some reason. What am I doing wrong?
Note that this is probably the first time I've tried doing anything this complicated with MySQL, and my little knowledge is probably more dangerous than being completely oblivious, so let me know if I'm going about this the wrong way completely (although I really, really don't want a stored procedure for this).
Unfortunately you can't use LOOP outside of a stored program: stored procedures, stored functions, and triggers.
You do have some options:
You can create a stored procedure and restrict the privileges so other users can't execute it.
Another option is to create a stored procedure temporarily in your script, run it, then drop it at the end of the script.
Otherwise, if you still don't want to create a stored procedure, your best bet is to write a small script in shell, python, etc to do your looping.
Good luck!