Extension to Ext.data.proxy.Sql to allow specifying JOINs You are free to use this code in any of your projects (open source or otherwise). I would appreciate if you mentioned my name (Andrei Tchijov @ Leaping Bytes, LLC) if you do.

SqlJoinProxy.js

Ext.define('LB.store.SqlJoinProxy', {
    alias: 'proxy.sqljoin',
    extend: 'Ext.data.proxy.Sql',

    config: {
        /**
         * config below will join table image ON image_id = i.id and will select field image_thumbnail as thumbnail and
         * field image_full_size as full_size
         * 
         * joins: [{
         *          'table' : 'image',
         *          'alias' : 'i',
         *          'foreignKey' : 'image_id',
         *          'fields' : {
         *              'thumbnail' : 'image_thumbnail',
         *              'full_size' : 'image_full_size'
         *          }
         * }]
         */
        joins: []
    },

    buildJoinedSQL: function(joins, mainAlias) {
        var result = {
            'fields' : '',
            'joins' : ''
        };

        for (var i = 0; i < joins.length; i++) {
            var join = joins[i];
            result.joins += ' LEFT JOIN ' + join.table + ' ' + join.alias + ' ON ( ' + join.alias + '.id = ' + mainAlias + '.' + join.foreignKey + ') ';

            for(var f in join.fields) {
                result.fields += ', ' + join.alias + '.' + f + ' as ' + join.fields[f];
            }
        }

        return result;
    },

    selectRecords: function(transaction, params, callback, scope) {
        var me = this,
            table = me.getTable(),
            idProperty = me.getModel().getIdProperty(),
            join_sqls = me.buildJoinedSQL(me.getJoins(), 't'),
            sql = 'SELECT t.* ' + join_sqls.fields + ' FROM ' + table + ' t ' + join_sqls.joins,
            records = [],
            filterStatement = ' WHERE ',
            sortStatement = ' ORDER BY ',
            i, ln, data, result, count, rows, filter, sorter, property, value;

        result = new Ext.data.ResultSet({
            records: records,
            success: true
        });

        if (!Ext.isObject(params)) {
            sql += filterStatement + 't.' + idProperty + ' = ' + params;
        } else {
            ln = params.filters && params.filters.length;
            if (ln) {
                for (i = 0; i < ln; i++) {
                    filter = params.filters[i];
                    property = filter.getProperty();
                    value = filter.getValue();
                    if (property !== null) {
                        property = property.indexOf('.') > 0 ? property : 't.' + property;
                        sql += filterStatement + property + ' ' + (filter.getAnyMatch() ? ('LIKE \'%' + value + '%\'') : ('= \'' + value + '\''));
                        filterStatement = ' AND ';
                    }
                }
            }

            ln = params.sorters && params.sorters.length;
            if (ln) {
                for (i = 0; i < ln; i++) {
                    sorter = params.sorters[i];
                    property = sorter.getProperty();
                    if (property !== null) {
                        property = property.indexOf('.') > 0 ? property : 't.' + property;
                        sql += sortStatement + property + ' ' + sorter.getDirection();
                        sortStatement = ', ';
                    }
                }
            }

            // handle start, limit, sort, filter and group params
            if (params.page !== undefined) {
                sql += ' LIMIT ' + parseInt(params.start, 10) + ', ' + parseInt(params.limit, 10);
            }
        }

        transaction.executeSql(sql, null,
            function(transaction, resultSet) {
                rows = resultSet.rows;
                count = rows.length;

                for (i = 0, ln = count; i < ln; i++) {
                    data = rows.item(i);
                    records.push({
                        clientId: null,
                        id: data[idProperty],
                        data: data,
                        node: data
                    });
                }

                result.setSuccess(true);
                result.setTotal(count);
                result.setCount(count);

                if (typeof callback == 'function') {
                    callback.call(scope || me, result)
                }
            },
            function(transaction, errors) {
                result.setSuccess(false);
                result.setTotal(0);
                result.setCount(0);

                if (typeof callback == 'function') {
                    callback.call(scope || me, result)
                }
            }
        );
    }
});