Question

我正在尝试创建一个数据库视图，其中包含有关马匹的信息，更具体地说是有关马匹，其主人和寄宿生的信息。该视图必须连接三个表。我必须创建“名字，姓氏，主要电话和谷仓名称”的视图。然后，我必须联接表“ boarder，horse和boarder_horse”来创建关系。我不知道如何将各个表连接在一起。

到目前为止，这就是我所拥有的：

CREATE VIEW horse_owner
AS
SELECT b.boarder firstname, b.boarder lastname, b.boarder primaryphone, 
h.horse barname

FROM boarder b
INNER JOIN horse h
ON bh.horse_id = h.id
INNER JOIN boarder_horse
ON bh.boarder_id = b.id

ORDER BY LastName DESC;

我不明白如何正确地将适当的表链接在一起。

Answer 1

您有// Import node's filesystem tools const fs = require('fs'); const path = require('path'); // variable definitions const a = 1; const b = 'hello'; const d = 'text'; const x = 0; const y = []; const z = 'hi' const arr = [1, 2, a, b, {c: d}, [x, y, z], '1a'] // reduce goes through the array and adds every element together from start to finish // using the function you provide const filedata = arr.reduce((a, b) => { // manually convert element to string if it is an object a = a instanceof Object ? JSON.stringify(a) : a; b = b instanceof Object ? JSON.stringify(b) : b; return a + '\r\n' + b; }); // path.resolve combines file paths in an OS-independent way // __dirname is the directory of the current .js file const filepath = path.resolve(__dirname, 'filename.txt'); fs.writeFile(filepath, filedata, (err) => { // this code runs after the file is written if(err) { console.log(err); } else { console.log('File successfully written!'); } });个错误的订单。另外，您缺少别名JOIN。试试：

bh

创建连接多个表的视图

1 个答案: