The meaning of [$@var-name] use in mysql ExtractValue() function -

- 

@xml= '<a><b>x</b><b>y</b></a>';  set @i=1,@j=2; select extractvalue(@xml,'//b[$@i]');

i know meaning of $@ use in function.

$@ stands user variable. see mysql documentation: user variables (weak checking)

first of in posted code @xml= 'xy'; not valid xml.

to explain, //b[$@i] xpath query. in $@i kind of variable interpolation. example documentation,

set @xml = '<a><b>x</b><b>y</b></a>'; set @i =1;

then doing select extractvalue(@xml, '//b[$@i]'); returns x sine says

select first ([1] index) tag element b. here, '//b[$@i]' nothing saying '//b[1]'


Comments

Post a Comment

Popular posts from this blog

javascript - gulp-nodemon - nodejs restart after file change - Error: listen EADDRINUSE events.js:85 -

-
i'm running nodejs 0.12.3 - gulp 3.10.8 , gulp-nodemon 2.0.3. gulpfile.js : gulp.task('serve', ['build'], function() { gulp.start('fb-flo'); nodemon({ script: paths.server, env: { 'node_env': 'development' }, // env: { 'node_env': 'production' }, execmap: { 'js': 'node_modules/babel/bin/babel-node --stage 1' //es7 cote server }, delay: '0ms', watch: ['src/shared/', 'src/server/'], ignore: ['src/shared/components'], tasks: function (changedfiles) { var tasks = []; changedfiles.foreach(function (file) { if (path.extname(file) === '.jsx' && !~tasks.indexof('bundlejs')) tasks.push('bundlejs'); if (path.extname(file) === '.less' && !~tasks.indexof('compileless')) tasks.push('compileless'); }); return tasks; } ...
Read more

Fatal Python error: Py_Initialize: unable to load the file system codec. ImportError: No module named 'encodings' -

-
i trying make simple python program opening list of webpages user manually download reports site. don't have previous experience preparing exe files.. , i'm in learning process python coding. of done on windows 7 x64 this python code: #!c:/python34/python.exe -u splinter import * import time import os import csv #---------------------------------- raporty = [] open('../raporty.csv', newline='') csvfile: contents = csv.reader(csvfile, delimiter=' ', quotechar='|') row in contents: r = ', '.join(row) r = r.replace(',','') raporty.append(r) #--not implemented yet zmienne = [] open('../zmienne.csv', newline='') csvfile: contents = csv.reader(csvfile, delimiter=' ', quotechar='|') row in contents: r = ', '.join(row) r = r.replace(',','') zmienne.append(r) print("start") browser = browser(...
Read more

javascript - oscilloscope of speaker input stops rendering after a few seconds -

-
the following script reads audio user's microphone , renders oscilloscope on html canvas. the source taken example of mozilla developer network: visualizations web audio api and here fiddle: http://jsfiddle.net/b7j8pktp/ mozgetusermedia (note: code has no fork mechanism different browsers: works firefox) it works fine few seconds , stops rendering. whereas works totally stable: http://mdn.github.io/voice-change-o-matic/ the problem can reduced following code. microphone activation icon (next the address bar in firefox) disappears after 5 seconds: navigator.mozgetusermedia({audio: true}, function() {}, function() {} ); ( http://jsfiddle.net/b7j8pktp/2/ ) this known bug in firefox. take stream getusermedia call , hook window so: navigator.mozgetusermedia({audio: true}, function(stream) { window.stream = stream; // rest of code }, function err() { // handle error }); hopefully can fixed soon. problem we're f...
Read more