mysql C API使用

（1） Makefile

CC=gcc
CFLAGS=-Wall
INCLUDE=-I/usr/include/mysql
LDFLAGS=-L/usr/lib64/mysql -lmysqlclient
PROG=my_cnt
SRC=test_mysql.c
OBJS=$(patsubst %.c, %.o, $(SRC))

all: clean $(PROG)

clean:
    rm -f $(PROG) *.o

$(OBJS): $(SRC)
    $(CC) $(CFLAGS) $(INCLUDE) -c $<

$(PROG): $(SRC) $(OBJS)
    $(CC) $(CFLAGS) $(OBJS) -o $(PROG) $(LDFLAGS)

（2）test_mysql.c

include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "mysql.h"

void process_result_set(MYSQL *mysql, MYSQL_RES *result)
{
    MYSQL_ROW row;
    unsigned int num_fields;
    unsigned int i;

    num_fields = mysql_num_fields(result);
    while ((row = mysql_fetch_row(result)))
    {
        unsigned long *lengths;
        lengths = mysql_fetch_lengths(result);
        for(i = 0; i < num_fields; i++)
        {
            printf("[%.*s] ", (int) lengths[i],
                   row[i] ? row[i] : "NULL");
        }
        printf("\n");
    }
}

int main()
{
    int status = 0;
    int i = 0;

    MYSQL m;
    MYSQL *mysql = &m;
    MYSQL_RES *result = NULL;

    if (mysql_init(mysql) == NULL) {
        printf("mysql init failed\n");
        exit(1);
    }

    if (mysql_real_connect (mysql, host_name, user_name, password,
        db_name, port_num, socket_name, CLIENT_MULTI_STATEMENTS) == NULL) {
        printf("mysql_real_connect() failed\n");
        mysql_close(mysql);
        exit(1);
    }
    /* execute multiple statements */
    status = mysql_query(mysql,
                      "CREATE TABLE if not exists test_table(id INT);\
                      INSERT INTO test_table VALUES(10);\
                      UPDATE test_table SET id=20 WHERE id=10;\
                      SELECT * FROM test_table;\
                      delete from test_table where id < 10;\
                      select count(*) from test_table");
    if (status) {
        printf("Could not execute statement(s)\n");
        mysql_close(mysql);
        exit(0);
    }

    /* process each statement result */
    do {
        /* did current statement return data? */
        result = mysql_store_result(mysql);
        if (result) {
            /* yes; process rows and free the result set */
            process_result_set(mysql, result);
            mysql_free_result(result);
        } else          /* no result set or error */
        {
            if (mysql_field_count(mysql) == 0) {
                printf("%lld rows affected\n", mysql_affected_rows(mysql));
            } else  /* some error occurred */
            {
                printf("Could not retrieve result set\n");
                break;
            }
        }
        /* more results? -1 = no, >0 = error, 0 = yes (keep looping) */
        if ((status = mysql_next_result(mysql)) > 0)
            printf("Could not execute statement\n");
        printf("[%d]\n", ++i);
    } while (status == 0);

    mysql_close(mysql);
    return 0;
}