SQLite示例教程

使用SQLite创建数据库

*sqlite3_open(const char *filename, sqlite3 *ppDb)

如果 filename 参数是 NULL 或 ‘:memory:’，那么 sqlite3_open() 将会在 RAM 中创建一个内存数据库，这只会在 session 的有效时间内持续。

如果文件名 filename 不为 NULL，那么 sqlite3_open() 将使用这个参数值尝试打开数据库文件。如果该名称的文件不存在，sqlite3_open() 将创建一个新的命名为该名称的数据库文件并打开。

简单的来说就是会打开一个数据库文件，文件不存在就会创建一个对应名字的数据库文件

*sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char *errmsg)

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

sqlite3_close(sqlite3*)

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。

#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>int main(int argc, char* argv[])
{sqlite3 *db;char *zErrMsg = 0;int rc;//sqlite3_open 打开指定的数据库文件，文件不存在就创建一个新的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");}sqlite3_close(db);return  0;
}

$ gcc creat_db.c -l sqlite3
$ ./a.out
Opened database successfully
$ ls
a.out  creat_db.c  test.db

使用SQLite3创建一个数据表

#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 *///< 打开数据库文件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 *///< 建表语句定义/* 创建主键 */ //"ID INT PRIMARY KEY     NOT NULL," 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 *///< 返回程序生成的执行的任何返回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;
}

$ gcc creat_db_datebase.c -l sqlite3
$ ./a.out
Opened database successfully
Table created successfully

数据库内筒如下：

在上述数据表中插入数据

#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;/********************第一步，打开数据库文件，获取数据库文件操作句柄*************************/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");}/********************第二步、定义数据操作语句***********************/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 );";/********************第三步、执行建表语句建立数据表**********************/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;
}

$ ./a.out
Opened database successfully
Records created successfully

数据的获取

获取数据中需要用到回调函数的使用

typedef int (*sqlite3_callback)(
void*,    /* sqlite3_exec() 中第四个参数*/
int,      /* 行中的列数 */
char**,   /* 行中的字符串 */
char**    /* 列名的字符串数组*/
);

#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 SQL statement */sql = "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;
}

$ gcc creat_db_select.c -l sqlite3
$ ./a.out
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 20000.0Callback function called: ID = 2
NAME = Allen
AGE = 25
ADDRESS = Texas
SALARY = 15000.0Callback function called: ID = 3
NAME = Teddy
AGE = 23
ADDRESS = Norway
SALARY = 20000.0Callback function called: ID = 4
NAME = Mark
AGE = 25
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully

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;
}

执行结果

$ gcc creat_db_update.c -l sqlite3
$ ./a.out
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 25000.0   #原来是 2000Callback function called: ID = 2
NAME = Allen
AGE = 25
ADDRESS = Texas
SALARY = 15000.0Callback function called: ID = 3
NAME = Teddy
AGE = 23
ADDRESS = Norway
SALARY = 20000.0Callback function called: ID = 4
NAME = Mark
AGE = 25
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully

delate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;
}

执行结果

$ ./a.out
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 25000.0Callback function called: ID = 3
NAME = Teddy
AGE = 23
ADDRESS = Norway
SALARY = 20000.0Callback function called: ID = 4
NAME = Mark
AGE = 25
ADDRESS = Rich-Mond
SALARY = 65000.0Operation done successfully

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SQLite-C语言实战

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