如何在IndexedDB中进行JOIN类型的查询 [英] How do I do an JOIN-type query in IndexedDB

问题描述

我尝试按照 http://hacks上的教程进行操作. mozilla.org/2010/06/comparing-indexeddb-and-webdatabase/关于在IndexedDB中进行查询，但是它们的示例不起作用.

I have tried following the tutorial at http://hacks.mozilla.org/2010/06/comparing-indexeddb-and-webdatabase/ with regards to doing queries in IndexedDB, but their example does not work.

如何在IndexedDB中进行JOIN类型查询?我已经用索引设置了对象存储，但是我似乎无法获取语法?

How to I do a JOIN type query in IndexedDB? I have set my objectstores up with indexes, but I just cant seem to get the syntax?

推荐答案

IndexedDB是键值(文档)存储.它没有JOIN查询或查询多个对象存储.但是，您可以查询一个事务中的多个商店.这就是在IndexedDB中进行联接查询的方式.

IndexedDB is key-value (document) store. It doesn't have JOIN query or querying over multiple object store. However you can query multiple stores in a transaction. That is how suppose to make join query in IndexedDB.

我有一些书面建模关系 http://dev.yathit.com/ydn-db/schema.html 使用我的库.

I have a bit of writeup modeling relationship http://dev.yathit.com/ydn-db/schema.html using my library.

这里正在加入SELECT * FROM Supplier, Part WHERE Supplier.CITY = Part.CITY的查询.

var iter_supplier = new ydn.db.IndexValueIterator('Supplier', 'CITY');
var iter_part = new ydn.db.IndexValueIterator('Part', 'CITY');
var req = db.scan(function(keys, values) {
  var SID = keys[0];
  var PID = keys[1];
  console.log(SID, PID);
  if (!SID || !PID) {
    return []; // done
  }
  var cmp = ydn.db.cmp(SID, PID); // compare keys
  if (cmp == 0) {
    console.log(values[0], values[1]);
    return [true, true]; // advance both
  } else if (cmp == 1) {
    return [undefined, SID]; // jump PID cursor to match SID
  } else {
    return [PID, undefined]; // jump SID cursor to match PID
  }
}, [iter_supplier, iter_part]);

有关加入查询文章的详细信息.

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