sqlite3_exec（）函数归纳

一、sqlite3_exec函数介绍

sqlite3_exec是sqlite3的接口API函数

源码API接口截图

1.参数分析：

int sqlite3_exec(
        sqlite3*,                                  /* An open database */
        const char *sql,                           /* SQL to be evaluated */
        int (*callback)(void*,int,char**,char**),  /* Callback function */
        void *,                                    /* 1st argument to callback */
        char **errmsg                              /* Error msg written here */
);
 sqlite3*：打开的数据库			    const char *sql：要执行的sql语句
 int (*callback)(void*,int,char**,char**)：执行sql语句时对应的回调函数
 void *：回调函数的参数				char **errmsg：存放错误信息
           

2.回调函数分析：

int (*callback)(void*,int,char**,char**)；

||

int callback(void *arg, int column_size, char *column_value[], char *column_name[])

参数分析：void *arg：是sqlite3_exec函数的第四个参数		column_size：数据库的字段数
		column_value[]：列的值 						column_name：字段名字
           

源码解释：

3.使用demon

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

int callback(void *arg, int column_size, char *column_value[], char *column_name[]){
	static int count = 0;
	int i;
	printf("%s\n", (char *)arg);
	if(0 == count){
		for(i = 0; i < column_size; i++){
			printf("%-8s\t", column_name[i]);
		}
		printf("\n");
	}
	for(i = 0; i < column_size; i++){
		printf("%-8s\t", column_value[i]);
	}
	printf("\n");
	printf("size is %d \n",column_size);
	count++;
	printf("%d\n",count);
	return 0;
}


int main(int argc, const char **argv)
{
	sqlite3 *db = NULL;
	int ret;
	char sql[1024] = "\0";
	char *errmsg = NULL;
	if(argc < 5){
		fprintf(stderr, "please input:%s name id score sex\n", argv[0]);
		exit(EXIT_FAILURE);//异常退出
	}
	//step 1: 创建数据库
	ret = sqlite3_open("./student.db", &db);//存在打开，不存在创建
	if(SQLITE_OK != ret){
		fprintf(stderr, "sqlite3_open:%s\n", sqlite3_errmsg(db));
		exit(EXIT_FAILURE);//异常退出
	}
	//step 2: 建表
	sprintf(sql, "create table if not exists student (name text, id integer, score real ,sex text)");
	ret = sqlite3_exec(db, sql, NULL, NULL, &errmsg);
	if(SQLITE_OK != ret){
		fprintf(stderr, "create table:%s\n", sqlite3_errmsg(db));
		fprintf(stderr, "create table:%s\n", errmsg);
		exit(EXIT_FAILURE);//异常退出
	}
	//step3: 插入数据
	sprintf(sql, "insert into student (name, id, score, sex) values ('%s', '%s', '%s','%s')", argv[1], argv[2], argv[3], argv[4]);
	ret = sqlite3_exec(db, sql, NULL, NULL, &errmsg);
	if(SQLITE_OK != ret){
		fprintf(stderr, "insert into:%s\n", sqlite3_errmsg(db));
		fprintf(stderr, "insert into:%s\n", errmsg);
		exit(EXIT_FAILURE);//异常退出
	}
	//step4: 查询	
	sprintf(sql, "select * from student ");
	ret = sqlite3_exec(db, sql, callback, "callback msg", &errmsg);
	if(SQLITE_OK != ret){
		fprintf(stderr, "select:%s\n", sqlite3_errmsg(db));
		fprintf(stderr, "select:%s\n", errmsg);
		exit(EXIT_FAILURE);//异常退出
	}

	//last step :关闭数据库
	sqlite3_close(db);
	return 0;
}
           

运行结果：