linux下C连接mysql
insert.c
#include<stdio.h>
#include "/usr/include/mysql/mysql.h"//locate mysql.h查找路径
int main()
{
MYSQL conn;
int res;
mysql_init(&conn);
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,CLIENT_FOUND_ROWS))
{
printf("connection success\n");
res=mysql_query(&conn,"insert into student values('1010')");
//res=mysql_query(&conn,"update student set num=num+1");
//res=mysql_query(&conn,"delete from student where num=1003");
if(res)
{
printf("connection failed\n");
mysql_close(&conn);
}
else
{
printf("connection success\n");
mysql_close(&conn);
}
}
return 0;
}
编译：gcc -o insert insert.c `mysql_config --cflags --libs`
./insert
search.c
#include<stdio.h>
#include<stdlib.h>
#include "/usr/include/mysql/mysql.h"
void query_sql(char* sql)
{
MYSQL conn;
int res;
MYSQL_RES *res_ptr;
MYSQL_FIELD *field;
MYSQL_ROW result_row;
int row,column;
int i,j;
mysql_init(&conn);
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,0))
{
printf("数据库连接成功！\n");
mysql_query(&conn,"set names utf8");
res=mysql_query(&conn,sql);
if(res)
{
printf("mysql_query failed\n");
}
else
{
res_ptr=mysql_store_result(&conn);
if(res_ptr)
{
column=mysql_num_fields(res_ptr);
row=mysql_num_rows(res_ptr)+1;
printf("查询到%lu行\n",row);
for(i=0;field=mysql_fetch_field(res_ptr);i++)
{
printf("%s\t",field->name);
}
printf("\n");
for(i=1;i<row;i++)
{
result_row=mysql_fetch_row(res_ptr);
for(j=0;j<column;j++)
{
printf("%s\t",result_row[j]);
}
printf("\n");
}
}
}
mysql_close(&conn);
}
}
int main()
{
char *query="select * from student";
query_sql(query);
return 0;
}
编译：gcc -o search search.c `mysql_config --cflags --libs`
./insert
------------------------------------------------------------------------------------------
*************************************************************
总结：C连接mysql
***************************
1、首先得了解MYSQL
---------------
MYSQL
以下代码块是用来连接数据库的通讯过程
typedef struct st_mysql {
NET net; /* Communication parameters */
gptr connector_fd; /* ConnectorFd for SSL */
char *host,*user,*passwd,*unix_socket,
*server_version,*host_info,*info,*db;
unsigned int port,client_flag,server_capabilities;
unsigned int protocol_version;
unsigned int field_count;
unsigned int server_status;
unsigned long thread_id; /* Id for connection in server */
my_ulonglong affected_rows;
my_ulonglong insert_id; /* id if insert on table with NEXTNR */
my_ulonglong extra_info; /* Used by mysqlshow */
unsigned long packet_length;
enum mysql_status status;
MYSQL_FIELD *fields;
MEM_ROOT field_alloc;
my_bool free_me; /* If free in mysql_close */
my_bool reconnect; /* set to 1 if automatic reconnect */
struct st_mysql_options options;
char scramble_buff[9];
struct charset_info_st *charset;
unsigned int server_language;
} MYSQL;
-------------------
MYSQL_RES
这段代码返回查询结果的行。返回的数据称为“数据集”
typedef struct st_mysql_res {
my_ulonglong row_count;
unsigned int field_count, current_field;
MYSQL_FIELD *fields;
MYSQL_DATA *data;
MYSQL_ROWS *data_cursor;
MEM_ROOT field_alloc;
MYSQL_ROW row; /* If unbuffered read */
MYSQL_ROW current_row; /* buffer to current row */
unsigned long *lengths; /* column lengths of current row */
MYSQL *handle; /* for unbuffered reads */
my_bool eof; /* Used my mysql_fetch_row */
} MYSQL_RES;
------------------
MYSQL_ROW
这个结构是数据行的一个安全表示法。你无法使用以空字符结束的串，因为数据在这个串可以是二进制, 也许没有包括任何字符。
typedef struct st_mysql_field {
char *name; /* Name of column */
char *table; /* Table of column if column was a field */
char *def; /* Default value (set by mysql_list_fields) */
enum enum_field_types type; /* Type of field. Se mysql_com.h for types */
unsigned int length; /* Width of column */
unsigned int max_length; /* Max width of selected set */
unsigned int flags; /* Div flags */
unsigned int decimals; /* Number of decimals in field */
} MYSQL_FIELD;
**********************************
2、在mysql里用到的一些函数
mysql_init() 获得或初始化一个MYSQL结构。
mysql_real_connect() 连接一个MySQL服务器。
mysql_close() 关闭一个服务器连接。
mysql_query() 执行指定为一个空结尾的字符串的SQL查询。
mysql_store_result() 检索一个完整的结果集合给客户。
mysql_num_fields() 返回一个结果集合重的列的数量。
mysql_num_rows() 返回一个结果集合中的行的数量。
mysql_fetch_row() 从结果集合中取得下一行。
mysql_affected_rows() 返回被最新的UPDATE, DELETE或INSERT查询影响的行数。
********************************
3、C语言对单个表的操作
对于插入、删除、更新都是同一类型的，是直接在mysql里面的表里操作
模式：
MYSQL conn;//mysql连接
int res;
mysql_init(&conn);//初始化mysql连接conn
//连接成功
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,0))
{
//database成功
———————————————————
res= mysql_query(&conn) |
if(res) |
{ |
//table成功 |
} |
else |
{ |-->若删除...等可无，查询输出各个数 | 据，具体可由循环，如下。
//table失败 |
} |
. |
. |
. |
. _________________________________|
mysql_close(&conn);
}
else
{
printf("failed\n");
mysql_close(&conn);
}
查询输出mysql的数据
lie=mysql_num_fields(str);//在上面函数部分有解释
hang=mysql_num_rows(str);
for(i=0;field=mysql_fetch_field(str);i++)
{
printf("%s\t",field->name);
}
printf("\n");
for(i=0;i<hang;i++)
{
row=mysql_fetch_row(str);
for(j=0;j<lie;j++)
{
printf("%s\t",row[j]);
}
printf("\n");
}
----------------------------
实例：
#include<stdio.h>
#include<stdlib.h>
#include "/usr/include/mysql/mysql.h"
void indeup_mysql(char *sql);
void select_mysql(char *sql);
int main()
{
char *s1="insert into student values('1001')";
indeup_mysql(s1);
char *s2="delete from student where num=1017";
indeup_mysql(s2);
char *s3="update student set num=num+1";
indeup_mysql(s3);
char *s4="select * from student";
select_mysql(s4);
return 0;
}
void indeup_mysql(char *sql)
{
MYSQL conn;
int m;
mysql_init(&conn);
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,0))
{
printf("database success\n");
m=mysql_query(&conn,sql);
if(m)
{
printf("table failed\n");
mysql_close(&conn);
}
else
{
printf("table success\n");
mysql_close(&conn);
}
}
else
{
printf("database failed\n");
mysql_close(&conn);
}
}
void select_mysql(char *sql)
{
MYSQL conn;
int n,R,C,i,j;
MYSQL_RES *chaxun;
MYSQL_FIELD *field;
MYSQL_ROW row;
mysql_init(&conn);
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,0))
{
printf("database success\n");
n=mysql_query(&conn,sql);
if(n)
{
printf("table failed\n");
mysql_close(&conn);
}
else
{
printf("table success\n");
chaxun=mysql_store_result(&conn);
if(chaxun)
{
C=mysql_num_fields(chaxun);
R=mysql_num_rows(chaxun);
for(i=0;field=mysql_fetch_field(chaxun);i++)
{
printf("%s\t",field->name);
}
printf("\n");
for(i=0;i<R;i++)
{
row=mysql_fetch_row(chaxun);
for(j=0;j<C;j++)
{
printf("%s\t",row[j]);
}
printf("\n");
}
mysql_close(&conn);
}
else
{
printf("NULL\n");
mysql_close(&conn);
}
}
}
else
{
printf("database failed\n");
mysql_close(&conn);
}
}
*******************************
4、C对多表的各个操作
其操作方法与对单表类似，但在对多表执行的时候的命令不同。
在网上搜了很多，看的很多，起到作用的就是执行命令
#include<stdio.h>
#include<stdlib.h>
#include "/usr/include/mysql/mysql.h"
int main()
{
MYSQL conn;
int res,hang,lie,i,j;
MYSQL_FIELD *field;
MYSQL_RES *str;
MYSQL_ROW row;
mysql_init(&conn);
if(mysql_real_connect(&conn,"localhost","root","111111","sqlinkdb",0,NULL,0))
{
printf("database success\n");
//查询
res=mysql_query(&conn,"select table3.num,name,table3.score from table2,table3 where table3.num=table2.num;");
if(res)
{
printf("table failed\n");
mysql_close(&conn);
}
else
{
printf("connection success\n");
str=mysql_store_result(&conn);
if(str)
{
lie=mysql_num_fields(str);
hang=mysql_num_rows(str);
for(i=0;field=mysql_fetch_field(str);i++)
{
printf("%s\t",field->name);
}
printf("\n");
for(i=0;i<hang;i++)
{
row=mysql_fetch_row(str);
for(j=0;j<lie;j++)
{
printf("%s\t",row[j]);
}
printf("\n");
}
}
else
{
printf("failed\n");
}
mysql_close(&conn);
}
}
else
{
printf("database failed\n");
mysql_close(&conn);
}
return 0;
}
[root@nana mysqlink]# ./mian
database success
connection success
num name score
1003 rr 90
1004 tt 78
//删除
res=mysql_query(&conn,"delete table1 from table1,table2 where table1.num=table2.num");
//修改、更新
res=mysql_query(&conn,"update table2,table3 set table3.score=table2.score where table2.num=table3.num;");
//查询
res=mysql_query(&conn,"select table3.num,name,table3.score from table2,table3 where table3.num=table2.num;");
******************************
需要注意的地方：
①、查找mysql.h的路径，头文件要正确
用locate mysql.h查找
②、column 'XXXX' in field list is ambiguous
原因：表中包含共同字段'xxxx'
如：select name from a,b where a.id=b.id 因为a、b2表里都有name字段
解决：字段前加上具体表名，如： select a.name from a,b where a.id=b.id
③、编译时要注意gcc -o insert insert.c `mysql_config --cflags --libs`
这里不是单引号！！！
但是效率太低啊！！！！
修改后的
