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c 数据库修改某个值

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行业动态
2025-02-23
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在C语言中，使用SQL语句可修改数据库中的某个值，如 UPDATE table_name SET column_name=new_value WHERE condition;。

在C语言中，要修改数据库中的某个值，通常需要使用数据库提供的API或库函数，以下是一个示例，展示如何使用SQLite数据库来修改某个表中的值。

前提条件

1、安装SQLite：确保你的系统上已经安装了SQLite。

2、包含头文件：在你的C代码中包含sqlite3.h头文件。

示例代码

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
int callback(void *NotUsed, int argc, charargv, charazColName) {
    for (int i = 0; i < argc; i++) {
        printf("%s = %s
", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    printf("
");
    return 0;
}
int main() {
    sqlite3 *db;
    char *zErrMsg = 0;
    int rc;
    const char *sql;
    const char *data = "Callback function called";
    // 打开数据库
    rc = sqlite3_open("test.db", &db);
    if (rc) {
        fprintf(stderr, "Can't open database: %s
", sqlite3_errmsg(db));
        exit(0);
    } else {
        fprintf(stdout, "Opened database successfully
");
    }
    // 创建表
    sql = "CREATE TABLE IF NOT EXISTS EMPLOYEE(" 
          "ID INT PRIMARY KEY     NOT NULL," 
          "NAME           TEXT    NOT NULL," 
          "AGE            INT     NOT NULL," 
          "ADDRESS        CHAR(50)," 
          "SALARY         REAL );";
    
    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s
", zErrMsg);
        sqlite3_free(zErrMsg);
    } else {
        fprintf(stdout, "Table created successfully
");
    }
    // 插入数据
    sql = "INSERT INTO EMPLOYEE (ID,NAME,AGE,ADDRESS,SALARY) " 
          "VALUES (1, 'Alice', 30, 'Beijing', 60000);";
    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s
", zErrMsg);
        sqlite3_free(zErrMsg);
    } else {
        fprintf(stdout, "Records created successfully
");
    }
    // 修改数据
    sql = "UPDATE EMPLOYEE SET SALARY = 70000 WHERE ID = 1;";
    rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s
", zErrMsg);
        sqlite3_free(zErrMsg);
    } else {
        fprintf(stdout, "Record updated successfully
");
    }
    // 查询数据以验证修改
    sql = "SELECT * from EMPLOYEE;";
    rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s
", zErrMsg);
        sqlite3_free(zErrMsg);
    } else {
        fprintf(stdout, "Operation done successfully
");
    }
    // 关闭数据库连接
    sqlite3_close(db);
    return 0;
}