MySQL - VARCHAR

要通过 JavaScript 程序创建 Varchar 数据类型的列，我们需要使用 mysql2 库的 query() 函数执行"CREATE TABLE"语句，如下所示 -

sql = "CREATE TABLE customers (cust_Name VARCHAR(30), cust_Address varchar(50))";
con.query(sql);

要通过 Java 程序创建 Varchar 数据类型的列，我们需要使用 JDBC 函数 execute() 执行"CREATE TABLE"语句，如下所示 -

String sql = "CREATE TABLE customers (cust_Name VARCHAR(30), cust_Address varchar(50))";
statement.execute(sql);

要通过 Python 程序创建 Varchar 类型的列，我们需要使用 MySQL Connector/Python 的 execute() 函数执行"CREATE TABLE"语句，如下所示 -

sql = 'CREATE TABLE test_table (column1 VARCHAR(32765) NOT NULL, column2 VARCHAR(32766) NOT NULL)CHARACTER SET 'latin1' COLLATE LATIN1_DANISH_CI'
cursorObj.execute(sql)

var mysql = require("mysql2");
var con = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "password",
}); //连接到 MySQL

con.connect(function (err) {
  if (err) throw err;
  //   console.log("Connected successfully...!");
  //   console.log("--------------------------");
  sql = "USE TUTORIALS";
  con.query(sql);
 //create a customer table and use varchar data type with differenet size
  sql = "CREATE TABLE customers (cust_Name VARCHAR(30), cust_Address varchar(50)) ";
  con.query(sql);
 sql = `SELECT DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = 'customers' AND COLUMN_NAME = 'cust_Name'`;
  con.query(sql, function (err, result) {
    if (err) throw err;
    console.log(result);
  });
});  

输出

生成的输出如下 -

[ { DATA_TYPE: 'varchar' } ]

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class Varchar {
   public static void main(String[] args) {
      String url = "jdbc:mysql://localhost:3306/TUTORIALS";
      String username = "root";
      String password = "password";
      try {
         Class.forName("com.mysql.cj.jdbc.Driver");
         Connection connection = DriverManager.getConnection(url, username, password);
         Statement statement = connection.createStatement();
         System.out.println("Connected successfully...!");
        //varchar data types...!;
         String sql = "CREATE TABLE customers (cust_Name VARCHAR(30), cust_Address varchar(50))";
         statement.execute(sql);
         System.out.println("column of a varchar type created successfully...!");
         ResultSet resultSet = statement.executeQuery("DESCRIBE customers");
         while (resultSet.next()){
            System.out.println(resultSet.getString(1)+" "+resultSet.getString(2));
         }
         connection.close();
      } catch (Exception e) {
         System.out.println(e);
      }
   }
}  

输出

获得的输出如下所示 -

Connected successfully...!
column of a varchar type created successfully...!
cust_Name varchar(30)
cust_Address varchar(50)  

import mysql.connector
# 建立连接
connection = mysql.connector.connect(
    host='localhost',
    user='root',
    password='password',
    database='tut'
)
# 创建游标对象
cursorObj = connection.cursor()
# 创建带有 varchar 列的表
sql = '''
CREATE TABLE test_table (
column1 VARCHAR(32765) NOT NULL,
column2 VARCHAR(32766) NOT NULL
)
CHARACTER SET 'latin1' COLLATE LATIN1_DANISH_CI
'''
cursorObj.execute(sql)
print("The table is created successfully!")
# 向创建的表中插入数据
insert_query = "INSERT INTO test_table (column1, column2) VALUES (%s, %s)"
data_to_insert = ("History", "Geography")
cursorObj.execute(insert_query, data_to_insert)
# 插入操作后提交更改
connection.commit()
print("Rows inserted successfully.")
# 现在显示表记录
select_query = "SELECT * FROM test_table"
cursorObj.execute(select_query)
result = cursorObj.fetchall()
print("Table Data:")
for row in result:
    print(row)
cursorObj.close()
connection.close()  

输出

以下是上述代码的输出 -

The table is created successfully!
Rows inserted successfully.
Table Data:
('History', 'Geography')