Ubuntu18.04 sqlite3安装及其应用

ubuntu18.04 sqlite3安装及其应用

1. 安装sqlite3

sudo apt-get install sqlite3
sudo apt-get install libsqlite3-dev

2. 安装sqlite3可视化工具sqlitebrowser

sudo apt-get install sqlitebrowser

3. sqlite3简单应用

#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: \n", (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 = NULL;char *zErrMsg = 0;int  rc;char *sql;const char* data = "Callback function called";/* Open database */int len = sqlite3_open("sqlite3demo", &db);if(len){fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));sqlite3_close(db);exit(0);}else{printf("You have opened a sqlite3 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, NULL, NULL, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Table created successfully\n\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, NULL, NULL, &zErrMsg);if( rc != SQLITE_OK ){fprintf(stderr, "SQL error: %s\n", zErrMsg);sqlite3_free(zErrMsg);}else{fprintf(stdout, "Records created successfully\n\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\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\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\n");}int nrow=0;int ncolumn = 0;char **azResult=NULL;       //二维数组存放结果/* Create merged SQL statement */sql="SELECT * from COMPANY";sqlite3_get_table( db , sql , &azResult , &nrow , &ncolumn , &zErrMsg );printf("nrow = %d ncolumn = %d\n", nrow, ncolumn);printf("the result is:\n");for(int i = 0; i < (nrow + 1) * ncolumn; i++){printf("azResult[%d]=%s\n", i, azResult[i]);}sqlite3_free_table(azResult);sqlite3_close(db);return 0;
}

1. sqlite3_open函数

int sqlite3_open(const char *filename,   /* Database filename (UTF-8) */sqlite3 **ppDb          /* OUT: SQLite db handle */
);

该函数打开一个指向 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。

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。

2. sqlite3_exec函数

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 */
);

该函数提供了一个执行 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。
如果一些语句不需要回调函数可以直接写NULL。
如：sqlite3_exec(db, sql, NULL, NULL, &zErrMsg)

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。

3. sqlite3_close函数

int sqlite3_close(sqlite3*);

该函数关闭之前调用 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。

4. sqlite3_get_table，sqlite3_free_table函数

int sqlite3_get_table(sqlite3 *db,          /* An open database */const char *zSql,     /* SQL to be evaluated */char ***pazResult,    /* Results of the query */int *pnRow,           /* Number of result rows written here */int *pnColumn,        /* Number of result columns written here */char **pzErrmsg       /* Error msg written here */
);void sqlite3_free_table(char **result);

该函数不使用回调函数进行数据查询。

对比可以发现nrow=3代表三行，ncolumn=5代表有五列。
加上最上面一行，一共4*5=20个数据，存储在azResult数组中。

参考资料：

SQLite - C/C++ | 菜鸟教程
linux下C语言编程操作数据库（sqlite3）