[linux c]mysql 编程笔记
要进行linux下的mysql的C编程，需要安装mysql及mysql的开发包，ubuntu下直接apt-get install libmysql++安装开发包。
#include <mysql.h>
相关函数:
MYSQL *mysql_init(MYSQL *); //这里称之为载入函数吧，返回的MYSQL指针要用到后续的函数中 int mysql_options(MYSQL *connection, enum option_to_set,const char *argument); //设置MYSQL*的一些属性，比如超时时间等 MYSQL *mysql_real_connect(MYSQL *connection, const char *server_host, const char *sql_user_name, const char *sql_password, const char *db_name, unsigned int port_number,//置0连接默认端口，一般为3306 const char *unix_socket_name,//NULL unsigned int flags);//无另外属性时置0 //连接函数 void mysql_close(MYSQL *connection); //关闭连接 unsigned int mysql_errno(MYSQL *connection); //返回错误代码 char *mysql_error(MYSQL *connection); //返回错误信息 int mysql_query(MYSQL *connection, const char *query); //执行sql语句 my_ulonglong mysql_affected_rows(MYSQL *connection); //返回执行语句过后受影响的行数 MYSQL_RES *mysql_store_result(MYSQL *connection); //返回执行结果，适用于数据量较小时 my_ulonglong mysql_num_rows(MYSQL_RES *result); //返回上面函数返回结果的行数 MYSQL_ROW mysql_fetch_row(MYSQL_RES *result); //抽取一条记录，返回NULL时表示抽取完记录或者错误 void mysql_data_seek(MYSQL_RES *result, my_ulonglong offset); //调整数据位置，offset为0时，下次调用mysql_fetch_row将返回result第一条记录 MYSQL_ROW_OFFSET mysql_row_tell(MYSQL_RES *result); //返回当前的位置 MYSQL_ROW_OFFSET mysql_row_seek(MYSQL_RES *result, MYSQL_ROW_OFFSET offset); //移动数据位置，并返回先前的位置，可以和上一个函数结合使用 void mysql_free_result(MYSQL_RES *result); //释放result空间 MYSQL_RES *mysql_use_result(MYSQL *connection); //返回执行结果，适用于数据量较大时 unsigned int mysql_field_count(MYSQL *connection); //返回查询结果中的列数（column数） MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result); //获得查询结果中的列名等信息（表头信息）
例子：
创建测试数据库
mysql> create database test;
创建用户
mysql> grant all on test.* to test@'localhost' identified by 'test';
sql文件：
-- -- Create the table children -- CREATE TABLE children ( childno int(11) NOT NULL auto_increment, fname varchar(30), age int(11), PRIMARY KEY (childno) ); -- -- Populate the table ‘children’ -- INSERT INTO children(childno,fname,age) VALUES(1,'Jenny',21); INSERT INTO children(childno,fname,age) VALUES(2,'Andrew',17); INSERT INTO children(childno,fname,age) VALUES(3,'Gavin',8); INSERT INTO children(childno,fname,age) VALUES(4,'Duncan',6); INSERT INTO children(childno,fname,age) VALUES(5,'Emma',4); INSERT INTO children(childno,fname,age) VALUES(6,'Alex',15); INSERT INTO children(childno,fname,age) VALUES(7,'Adrian',9);
导入sql文件：
mysql -u test --password=test test<mysqlchildren.sql
导入后的情况：
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| children |
+----------------+
1 row in set (0.00 sec)
mysql> select * from children;
+---------+--------+------+
| childno | fname | age |
+---------+--------+------+
| 1 | Jenny | 21 |
| 2 | Andrew | 17 |
| 3 | Gavin | 8 |
| 4 | Duncan | 6 |
| 5 | Emma | 4 |
| 6 | Alex | 15 |
| 7 | Adrian | 9 |
+---------+--------+------+
7 rows in set (0.00 sec)
C代码:
#include <stdio.h> #include <stdlib.h> #include <mysql.h> MYSQL *mysql_main; MYSQL_RES *res_ptr; MYSQL_ROW sqlrow; void display_header(); void display_row(); int main(int argc,char *argv[]) { int res; int first_row = 1; mysql_main = mysql_init(NULL); if(!mysql_main) { fprintf(stderr,"mysql_init failed\n"); return EXIT_FAILURE; } mysql_main = mysql_real_connect(mysql_main,"localhost","test","test","test",0,NULL,0); if(mysql_main) { printf("Connection success:\n"); res = mysql_query(mysql_main,"SELECT childno,fname,age FROM children WHERE age>5"); if(res) { fprintf(stderr,"SELECT error: %s\n",mysql_error(mysql_main)); } else { res_ptr = mysql_use_result(mysql_main); if(res_ptr) { while((sqlrow = mysql_fetch_row(res_ptr))) { if(first_row) { display_header(); first_row = 0; } display_row(); } } } } else { printf("Connection failed\n"); } mysql_close(mysql_main); return EXIT_SUCCESS; } void display_header() { MYSQL_FIELD *field_ptr; printf("Column details:\n"); while((field_ptr = mysql_fetch_field(res_ptr))!=NULL) { printf("\t Name: %s\n",field_ptr->name); printf("\t Type: "); if(IS_NUM(field_ptr->type)) { printf("Numeric filed\n"); } else { switch(field_ptr->type) { case FIELD_TYPE_VAR_STRING: printf("VARCHAR\n"); break; case FIELD_TYPE_LONG: printf("LONG\n"); break; default: printf("Type is %d,check in mysql_com.h\n",field_ptr->type); } } printf("\t MAX width %ld\n",field_ptr->length); if(field_ptr->flags&AUTO_INCREMENT_FLAG) printf("\t Auto increments\n"); printf("\n"); } } void display_row() { unsigned int field_count; field_count = 0; while(field_count<mysql_field_count(mysql_main)) { if(sqlrow[field_count]) printf("%s ",sqlrow[field_count]); else printf("NULL"); field_count++; } printf("\n"); }
gcc -I/usr/include/mysql -L/usr/lib/mysql -lmysqlclient -o mysqltest mysqltest.c
./test
结果如下：
Connection success:
Column details:
Name: childno
Type: Numeric filed
MAX width 11
Auto increments
Name: fname
Type: VARCHAR
MAX width 30
Name: age
Type: Numeric filed
MAX width 11
1 Jenny 21
2 Andrew 17
3 Gavin 8
4 Duncan 6
6 Alex 15
7 Adrian 9
