Simple data query for getting started with MySQL

mysql_init initializes the database link – gets a link mysql_real_connect connects to the database server and executes the mysql_query query – the query statement is a string that retrieves each row separately mysql_store_result – the results are stored in the link and are a one-time query. Get the table header from the result set Information – mysql_fetch_fields – header information is stored in the memory space pointed to by the MYSQL_FIELD type pointer. Parse the header – mysql_field_count to obtain the number of columns. The for loop parses column by column. mysql_fetch_row obtains data row by row from the result set and releases memory after parsing each column for each row. Space

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Specific code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include <mysql/mysql.h>
int main()
{
    int     ret = 0;
    int     i = 0;
    MYSQL   mysql;
    MYSQL   *con = NULL;
    unsigned int fieldnum;  
    printf("hello....\n");
    con = mysql_init(&mysql);
    if (con == NULL)
    {
        ret = mysql_errno(&mysql);
        printf("func mysql_init() err :%d\n", ret);
        return ret;
    }
    con = mysql_real_connect(&mysql, "localhost", "root", "123456", "mydb2", 0, NULL, 0 );
    if (con == NULL)
    {
        ret = mysql_errno(&mysql);
        printf("func mysql_real_connect() err :%d\n", ret);
        return ret;
    }
    else
    {
        printf("func mysql_real_connect() ok\n");
    }
    //执行sql查询
    mysql_query(&mysql, "set names utf8");//解决中文乱码
    char *sql = "select *from employee";
    ret = mysql_query(&mysql, sql);
    if (ret != 0)
    {
        ret = mysql_errno(&mysql);
        printf("func mysql_query() err :%d\n", ret);
        return ret;
    }
    /*
    //获取结果集 一次性获取
    MYSQL_RES * sqlres =mysql_store_result( &mysql);
    if (sqlres == NULL)
    {
        ret = mysql_errno(&mysql);
        printf("func mysql_store_result() err :%d\n", ret);
        return ret;
    }
    */
    //对每一行分别进行检索
    MYSQL_RES * sqlres =mysql_store_result(&mysql);
    if (sqlres == NULL)
    {
        ret = mysql_errno(&mysql);
        printf("func mysql_store_result() err :%d\n", ret);
        return ret;
    }
    //从结果集，获取表头信息
    MYSQL_FIELD *fields = mysql_fetch_fields(sqlres);
    fieldnum = mysql_field_count(&mysql);
    for (i=0; i<fieldnum; i++)
    {
        printf("%s\t", fields[i].name);
    }
    printf("\n");
    //从结果集， 按照行获取信息信息
    MYSQL_ROW row = NULL; //(char **)
    //从结果集中一行一行的获取数据
    while (  row = mysql_fetch_row(sqlres))
    {
        fieldnum = mysql_field_count(&mysql); 
        //优化，我的行有多少列。。。。查找这样的api函数
        for (i=0; i<fieldnum; i++) //经过测试 发现 不是以0结尾的指针数组。。
        {
            printf("%s\t", row[i]);
        }
        printf("\n");
    }
    mysql_free_result(sqlres);
    mysql_close(&mysql);
    return ret;
}

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