在PostgreSQL中使用JSONB对象数组

数据库提示 (Database Tips)

In my last article, we focused on turning a PostgreSQL jsonb column, that contained an Array of Objects, into a recordset, so that it could be queried in a relational manner.

在我的上一篇文章中，我们专注于将包含对象数组的PostgreSQL jsonb列转换为记录集，以便可以以关系方式对其进行查询。

我们将要做什么 (What We Will Do)

In this article, I’d like to continue our work with a jsonb column containing an Array of Objects and explore how to,

在本文中，我想继续研究包含对象数组的jsonb列，并探讨如何实现这一点，

• Get all Objects in the Array.
  获取数组中的所有对象。
• Get a specific Object from the Array by position in the Array. When the position is known and when we have to discover it.
  通过在数组中的位置从数组中获取特定的对象。 何时知道位置以及何时必须找到它。
• Add a json Object to the Array.
  向数组添加一个json对象。
• Remove a specific Object from the Array.
  从阵列中删除特定的对象。

We will not only look at the query techniques but think about these as being API end-points and what they might mean for the front-end in, say, a PERN stack.

我们不仅会研究查询技术，还将这些技术视为API端点，以及它们对PERN堆栈中的前端可能意味着什么。

Sample Data

样本数据

Our sample data in a jsonb column will look similar to this,

我们在jsonb列中的示例数据看起来与此类似，

[{
       
  "productid": 3,
  "name": "Virtual Keyboard",
  "price": 150}, {
       
  "productid": 1,
  "name": "Dell 123 Laptop Computer",
  "price": 1300},
 {
       
  "productid": 8,
  "name": "LG Ultrawide Monitor",
  "price": 190}
]

This might represent products purchased by a customer. We want to Add new purchases, Get all items purchased, Get a specific item purchased and Remove an item purchased.

这可能代表客户购买的产品。 我们要添加新购买，购买所有物品，购买特定物品并删除购买的物品。

In the last article we worked with the jsonb_to_recordset() function.

在上一篇文章中，我们使用了jsonb_to_recordset()函数。

In this article, we will make extensive use of the jsonb_array_elements() function.

在本文中，我们将广泛使用jsonb_array_elements()函数。

假设条件 (Assumptions)

I will assume you have PostgreSQL and something along the lines of pgAdmin.

我将假设您拥有PostgreSQL和pgAdmin之类的东西。

让我们开始吧！ (Let’s Get Started!)

建立我们的数据 (Building Our Data)

1. Open pgAdmin and create a database as desired.

   打开pgAdmin并根据需要创建数据库。

2. Right-Click on the database name and choose Query Tool.

   右键单击数据库名称，然后选择“ 查询工具” 。

3. Run the snippet below to create a simple table that will have an id, purchaser name and a jsonb column that stores an array of json objects, which will store items purchased.

   运行下面的代码片段以创建一个简单的表，该表将具有一个id，购买者名称和一个jsonb列，该列存储json对象数组，该数组将存储购买的商品。

CREATE TABLE public.purchases
(
    id   serial PRIMARY KEY,
    purchaser varchar(50),
    items_purchased jsonb
);

4. Run the snippet below to insert four records in to the table.

4.运行下面的代码片段，将四个记录插入到表中。

INSERT INTO purchases (purchaser,items_purchased) VALUES ('Bob',
'[{
       
  "productid": 1,
  "name": "Dell 123 Laptop Computer",
  "price": 1300},
 {
       
  "productid": 2,
  "name": "Mechanical Keyboard",
  "price": 120}
]');INSERT INTO purchases (purchaser,items_purchased) VALUES('Carol',
'[{
       
  "productid": 3,
  "name": "Virtual Keyboard",
  "price": 150}, {
       
  "productid": 1,
  "name": "Dell 123 Laptop Computer",
  "price": 1300},
 {
       
  "productid": 8,
  "name": "LG Ultrawide Monitor",
  "price": 190}
]');INSERT INTO purchases (purchaser,items_purchased) VALUES ('Ted',
'[{
       
  "productid": 6,
  "name": "Ergonomic Keyboard",
  "price": 90},
 {
       
  "productid": 7,
  "name": "Dell 789 Desktop Computer",
  "price": 120}
]');INSERT INTO purchases (purchaser,items_purc