[英]Update an item in Dynamodb?
我是這項技術的新手。 所以請忍受我下面的解釋。
我的用例:
我正在根據主鍵(ID)更新 Dynamodb 中的項目。 基本上我的記錄有 4 列( ID, description, name , price )。
這里的問題是假設當我有一個鍵為 123 的項目時
ID description name price
123 Model nokia 10
當我使用上面的 lamda 函數更新所有列時,它工作正常。 但是當我嘗試僅更新description
列時,它會拋出 'ExpressionAttributeValues can't be empty` 的錯誤。 所以為此我做了這樣的事情
ExpressionAttributeValues:{
":d":event.description ? event.description : null ,
":n":event.name ? event.name : null,
":p":event.price ? event.price : null
}
但問題是它會更新我給出的唯一值。 就像如果我只對modal1
給出了description
,那么它會改變它並給出這樣的結果
ID description name price
123 Model1 null null
這是正確的,因為上面的代碼片段說要這樣做。
我想實現什么?
我怎樣才能改變這種行為來實現這樣的目標
ID description name price
123 Model1 nokia 10
任何幫助表示贊賞
更新代碼
var AWS = require("aws-sdk");
AWS.config.update({
region: "regionname",
endpoint: "endpointurl"
});
var docClient = new AWS.DynamoDB.DocumentClient()
var tablename = "Example";
var UpdateExpression = "'set";
var ExpressionAttributeValues= {};
var ExpressionAttributeNames= {};
var ID = "xx";
var description = "Iphone";
var name = "xx";
var price = 50;
var params = {
TableName: tablename,
Key:{
"ID": ID
}
};
docClient.update(params,onUpdate);
function onUpdate(err) {
if (err) {
console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2));
} else {
console.log("Update succeeded.");
}
if(description) {
UpdateExpression = UpdateExpression + " description = :d,",
ExpressionAttributeValues [":d"] = description ,
console.log("first...")
}
if(name){
UpdateExpression = UpdateExpression + " #na = :n,",
ExpressionAttributeNames['#na'] = 'name' ,
ExpressionAttributeValues[":n"] = name ,
console.log("second...")
}
if(price){
UpdateExpression = UpdateExpression + " price = :p',",
ExpressionAttributeValues[":p"] = price ,
console.log("third...")
}
console.log(UpdateExpression)
console.log(ExpressionAttributeNames)
console.log(ExpressionAttributeValues)
return (UpdateExpression,ExpressionAttributeNames,ExpressionAttributeValues)
}
當我運行代碼時,我得到了這樣的輸出:
D:\\Dynamo>node FullUpdate.js
Update succeeded.
first...
second...
third...
'set description = :d, #na = :n, price = :p',
{ '#na': 'name' }
{ ':d': 'Iphone', ':n': 'xx', ':p': 50 }
你必須根據你擁有的變量來構造你的查詢,所以你必須做這樣的事情
UpdateExpression = "set";
ExpressionAttributeValues: {};
ExpressionAttributeNames: {};
if(event.description){
UpdateExpression = UpdateExpression + "description = :d";
ExpressionAttributeValues[":d"] = event.description
}
if(event.name){
UpdateExpression = UpdateExpression + "#na = :n";
ExpressionAttributeNames['#na'] = 'name'
ExpressionAttributeValues[":d"] = event.name
}
if(event.price){
UpdateExpression = UpdateExpression + "price = :p";
ExpressionAttributeValues[":d"] = event.pice
}
小心逗號,並記錄您的查詢以確保它符合您的期望。 您可以檢查我為此目的使用的功能,
update(_id, store_id, opts?) {
var Key = {
_id: _id,
store_id: store_id
};
if (Object.keys(opts).length > 0) {
let UpdateExpression =
"SET #date = :date, #author = :author";
let ExpressionAttributeNames = {
"#date": "date",
"#author": "author"
}
let ExpressionAttributeValues = {
":date": new Date().getTime(),
":author": localStorage.getItem('user_id')
}
if ((opts && opts.title)) {
UpdateExpression = UpdateExpression + "#title = :title,";
ExpressionAttributeNames["#title"] = "title";
ExpressionAttributeValues[":title"] = opts.title
}
if ((opts && opts.category)) {
UpdateExpression = UpdateExpression + "#category = :category,";
ExpressionAttributeNames["#category"] = "category";
ExpressionAttributeValues[":category"] = opts.category
}
if ((opts && opts.category)) {
UpdateExpression = UpdateExpression + "#dimension = :dimension,";
ExpressionAttributeNames["#dimension"] = "dimension";
ExpressionAttributeValues[":dimension"] = opts.dimension
}
if ((opts && opts.category)) {
UpdateExpression = UpdateExpression + "#destination = :destination,";
ExpressionAttributeNames["#destination"] = "destination";
ExpressionAttributeValues[":destination"] = opts.destination
}
if ((opts && opts.category)) {
UpdateExpression = UpdateExpression + "#timeStart = :timeStart,";
ExpressionAttributeNames["#timeStart"] = "timeStart";
ExpressionAttributeValues[":timeStart"] = opts.timeStart
}
if ((opts && opts.category)) {
UpdateExpression = UpdateExpression + "#timeEnd = :timeEnd,";
ExpressionAttributeNames["#timeEnd"] = "timeEnd";
ExpressionAttributeValues[":timeEnd"] = opts.timeEnd
}
if ((opts && opts.publish)) {
UpdateExpression = UpdateExpression + "#publish = :publish,"
ExpressionAttributeNames["#publish"] = "publish"
ExpressionAttributeValues[":publish"] = "x";
}
UpdateExpression = UpdateExpression.replace(new RegExp(',$'), '');
if ((opts && opts.nbviews)) {
UpdateExpression = UpdateExpression + "ADD #nbviews = :nbviews"
ExpressionAttributeNames["#nbviews"] = "nbviews"
ExpressionAttributeValues[":nbviews"] = 1;
}
if ((opts && !opts.publish)) {
UpdateExpression = UpdateExpression + " REMOVE #publish"
ExpressionAttributeNames["#publish"] = "publish"
}
return this.dataService.update(TABLENAME, Key, UpdateExpression, null, ExpressionAttributeNames, ExpressionAttributeValues);
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