SQLite C API如何将查询输出保存为字符串

#include <stdio.h>
#include <sqlite3.h>

// 回调函数，用于处理查询结果
static int callback(void* data, int argc, char** argv, char** azColName) {
    int i;
    for (i = 0; i < argc; i++) {
        // 将每个字段的值追加到字符串中
        strcat((char*)data, argv[i] ? argv[i] : "NULL");
        strcat((char*)data, " ");
    }
    strcat((char*)data, "\n");
    return 0;
}

int main() {
    sqlite3* db;
    char* errMsg = 0;
    char result[1000] = ""; // 用于保存查询结果的字符串

    // 打开数据库
    int rc = sqlite3_open(":memory:", &db);
    if (rc) {
        fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
        return 0;
    }

    // 创建表并插入数据
    rc = sqlite3_exec(db, "CREATE TABLE COMPANY(ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL, AGE INT NOT NULL, ADDRESS CHAR(50), SALARY REAL NOT NULL);"
                          "INSERT INTO COMPANY VALUES(1, 'Paul', 32, 'California', 20000.0);"
                          "INSERT INTO COMPANY VALUES(2, 'Allen', 25, 'Texas', 15000.0);"
                          "INSERT INTO COMPANY VALUES(3, 'Teddy', 23, 'Norway', 20000.0);"
                          "INSERT INTO COMPANY VALUES(4, 'Mark', 25, 'Rich-Mond', 65000.0);", 0, 0, &errMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s\n", errMsg);
        sqlite3_free(errMsg);
    }

    // 执行查询并将结果保存为字符串
    rc = sqlite3_exec(db, "SELECT * FROM COMPANY;", callback, (void*)result, &errMsg);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "SQL error: %s\n", errMsg);
        sqlite3_free(errMsg);
    }

    // 输出查询结果字符串
    printf("Query Result:\n%s", result);

    // 关闭数据库
    sqlite3_close(db);

    return 0;
}