嵌入式数据库之SQLite

1.SQLite简介

轻量化，易用的嵌入式数据库，用于设备端的数据管理，可以理解成单点的数据库。传统服务器型数据 库用于管理多端设备，更加复杂。

SQLite是一个无服务器的数据库，是自包含的。这也称为嵌入式数据库，这意味着数据库引擎作 为应用程序的一部分运行。 MySQL需要运行服务器，MySQL将需要客户端和服务器架构通过网络进行交互。

SQLite和MySQL的优缺点对比：

 基于嵌入式的数据库主要有：SQLite，Firebird，Berkeley DB，eXtremeDB

Firebird 是关系型数据库，功能强大，支持存储过程，SQL兼容等

SQLite 关系型数据库，体积小，支持ACID事务

Berkeley DB 并没有数据库服务器的概念，他的程序直接链接到应用程序中 eXtremeDB 是内存数据库，运行效率高

2 SQLite数据库安装

安装方式一：

 sudo apt-get -y install sqlite

安装方式二：

https://www.sqlite.org/download.html

1. 把下载的文件sqlite-autoconf-3390000.tar.gz上传到开发板
2. tar xvf sqlite-autoconf-3390000.tar.gz 解压
3. cd sqlite-autoconf-3390000 进入文件夹
4. ./configure --prefix=/usr/local 配置安装路径在/usr/local
5. make 编译//比较久10分钟
6. sudo make install 安装

安装成功过，运行sqlite3 进入SQL命令操作流程。

3.SQLite的命令用法

• 创建一个数据库

方式一：

1. sqlite3 进入数据库
2. .open test.db
3. .quit
数据库退出后在命令当前路径创建数据库test.db

方式二：

sqlite3 test.db //在命令运行当前窗口创建数据库test.db
在数据库命令下
.databases 列出当前打开的数据库
.quit 退出

• 创建一张表格

create table stu2(id Integer,name char,score Integer);

• 插入一条记录

insert into stu values(18130106,'huang',99);
insert into stu2 values(18130101,"gang",100); ''和""都行
insert into stu(name,score) values("huanggang",98); 插入部分字段内容

• 查看数据库的记录

select * from stu; //查询所有字段的结果
select name,score from stu; //查询数据库中部分字段的内容

• 删除一条记录

delete from stu where id = 18130101;

• 更改一条记录

update stu set name = 'huangg' where id = 18130106;

• 删除一张表

drop table stu;

• 增加一列

alter table stu add column sex char;

4.SQLite的编程操作

sqlite3_open(const char *filename, sqlite3 **ppDb)
该例程打开一个指向 SQLite 数据库文件的连接，返回一个用于其他 SQLite 程序的数据库连接对象。sqlite3_close(sqlite3*)
该例程关闭之前调用 sqlite3_open() 打开的数据库连接。所有与连接相关的语句都应在连接关闭之前完
成。
如果还有查询没有完成，sqlite3_close() 将返回 SQLITE_BUSY 禁止关闭的错误消息。const char *sqlite3_errmsg(sqlite3*);sqlite3_errcode() 通常用来获取最近调用的API接口返回的错误代码.

示例代码：

1、打开数据库：

#include <stdio.h>
#include <sqlite3.h>
int main(char argc, char **argv)
{sqlite3 *db;int ret;if(argc < 2){printf("Usage: %s xxx.db\n",argv[0]);return -1;}if( (ret = sqlite3_open(argv[1],&db)) == SQLITE_OK){printf("open %s success\n",argv[1]);}else{printf("error:%s,%d\n",sqlite3_errmsg(db),ret);if(ret == 14){printf("permission den\n");}return -1;}sqlite3_close(db);printf("done\n");return 0;
}

2、创建表的接口：

sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char
**errmsg)
该例程提供了一个执行 SQL 命令的快捷方式，SQL 命令由 sql 参数提供，可以由多个 SQL 命令组成。
在这里，第一个参数 sqlite3 是打开的数据库对象，sqlite_callback 是一个回调，data 作为其第一
个参数，errmsg 将被返回用来获取程序生成的任何错误。
sqlite3_exec() 程序解析并执行由 sql 参数所给的每个命令，直到字符串结束或者遇到错误为止。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

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>static int callback(void *NotUsed, int argc, char **argv, char **azColName){int i;for(i=0; i<argc; i++){printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");}printf("\n");return 0;
}
int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;char *sql;/* Open database */rc = sqlite3_open("test.db", &db);if( rc ){fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));exit(0);}else{fprintf(stdout, "Opened database successfully\n");}/* Create SQL statement */sql = "CREATE TABLE COMPANY(" \"ID INT PRIMARY KEY NOT NULL," \"NAME TEXT NOT NULL," \"AGE INT NOT NULL," \"ADDRESS CHAR(50)," \"SALARY REAL );";/* Execute SQL statement */rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Table created successfully\n");}sqlite3_close(db);return 0;
}

3、插入数据的接口

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *NotUsed, int argc, char **argv, char **azColName){int i;for(i=0; i<argc; i++){printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");}printf("\n");return 0;
}int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;char *sql;/* Open database */rc = sqlite3_open("test.db", &db);if( rc ){fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));exit(0);}else{fprintf(stderr, "Opened database successfully\n");}/* Create SQL statement */sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " \"VALUES (1, 'Paul', 32, 'California', 20000.00 ); " \"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " \"VALUES (2, 'Allen', 25, 'Texas', 15000.00 ); " \"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" \"VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );" \"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY)" \"VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );";/* Execute SQL statement */rc = sqlite3_exec(db, sql, callback, 0, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Records created successfully\n");}sqlite3_close(db);return 0;
}

4、select操作

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *data, int argc, char **argv, char **azColName){int i;fprintf(stderr, "%s: ", (const char*)data);for(i=0; i<argc; i++){printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");}printf("\n");return 0;
}int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;char *sql;const char* data = "Callback function called";/* Open database */rc = sqlite3_open("test.db", &db);/* Create SQL statement */sql = "SELECT * from COMPANY";/* Execute SQL statement */rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);sqlite3_close(db);return 0;
}

5、update操作：

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *data, int argc, char **argv, char **azColName){int i;fprintf(stderr, "%s: ", (const char*)data);for(i=0; i<argc; i++){printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");}printf("\n");return 0;
}
int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;char *sql;const char* data = "Callback function called";/* Open database */rc = sqlite3_open("test.db", &db);if( rc ){fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));exit(0);}else{fprintf(stderr, "Opened database successfully\n");}/* Create merged SQL statement */sql = "UPDATE COMPANY set SALARY = 25000.00 where ID=1; " \"SELECT * from COMPANY";/* Execute SQL statement */rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Operation done successfully\n");}sqlite3_close(db);return 0;
}

6、delect操作

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
static int callback(void *data, int argc, char **argv, char **azColName){int i;fprintf(stderr, "%s: ", (const char*)data);for(i=0; i<argc; i++){printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");}printf("\n");return 0;
}
int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;char *sql;const char* data = "Callback function called";/* Open database */rc = sqlite3_open("test.db", &db);if( rc ){fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));exit(0);}else{fprintf(stderr, "Opened database successfully\n");}/* Create merged SQL statement */sql = "DELETE from COMPANY where ID=2; " \"SELECT * from COMPANY";/* Execute SQL statement */rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Operation done successfully\n");}sqlite3_close(db);return 0;
}