Node.js MySQL 删除查询
原文:https://www.geeksforgeeks.org/node-js-mysql-delete-query/
我们使用 SQL DELETE Query 从 MySQL 表中删除带有某些条件的数据。
语法:
-
这将删除客户表的所有行，但其他所有内容将保持原样(索引等)。
js DELETE FROM users -
这将删除用户标识为 2 的用户表的所有行。
js DELETE FROM users WHERE userId = 2
模块:
-
mysql:处理 sql 连接和查询
js npm install mysql
SQL 用户表预览:
示例 1: 从用户表中删除所有行
java 描述语言
const mysql = require("mysql");
let db_con = mysql.createConnection({
host: "localhost",
user: "root",
password: '',
database: 'gfg_db'
});
db_con.connect((err) => {
if (err) {
console.log("Database Connection Failed !!!", err);
return;
}
console.log("We are connected to gfg_db database");
// here is our query
let query = 'DELETE FROM users';
db_con.query(query, (err, rows) => {
if(err) throw err;
console.log('Cleared users Table');
});
});
输出:
示例 2: 删除所有名称为‘pratik’的用户。
- 方法 1: 硬编码该值
java 描述语言
const mysql = require("mysql");
let db_con = mysql.createConnection({
host: "localhost",
user: "root",
password: '',
database: 'gfg_db'
});
db_con.connect((err) => {
if (err) {
console.log("Database Connection Failed !!!", err);
return;
}
console.log("We are connected to gfg_db database");
// This is our Hard Coded Query
let query = "DELETE FROM users WHERE name = 'pratik'";
db_con.query(query, (err, rows) => {
if(err) throw err;
console.log('Number of rows deleted = ' + rows.affectedRows);
});
});
- 方法 2: 动态查询
java 描述语言
const mysql = require("mysql");
let db_con = mysql.createConnection({
host: "localhost",
user: "root",
password: '',
database: 'gfg_db'
});
db_con.connect((err) => {
if (err) {
console.log("Database Connection Failed !!!", err);
return;
}
console.log("We are connected to gfg_db database");
// notice the ? in below query
let query = "DELETE FROM users WHERE name = ?";
// Dynamic Value
let name = 'pratik';
// Notice the name variable below
// It will replace the ? in query
db_con.query(query, name, (err, rows) => {
if(err) throw err;
console.log('Number of rows deleted = ' + rows.affectedRows);
});
});
输出:
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