需要在 C++ 程序中读写 sqlite3 数据库，查阅了一下资料，发现了一个简单实用教程。另外还有如何在windows下生成sqlite3静态库，生成好的sqlite3静态库可以在这里下载。
windows下生成sqlite3静态库
- 去 sqlite 官网下载页面下载源文件 sqlite-amalgamation-3180000.zip 。
- 在VS2013中，文件->新建->项目->Win32项目，命名为sqlite3(其他名称也行)。在向导设置中，选择DLL(D)、空项目。选择release x64模式。
- 将下载的sqlite-amalgamation-3180000.zip 中的“sqlite3.h”、“sqlite3.c”、“sqlite3ext.h”三个文件添加到工程中，具体做法：右键sqlite3工程->添加->现有项，在出现的对话框中选择上述三个文件。
- 编译生成sqlite3.dll文件，同时会在工程所在目录中产生sqlite3.obj文件。
- 接下来要用到VS安装目录下的lib.exe文件。将sqlite3.obj文件复制到lib.exe所在目录下，我的是C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\amd64。
- 打开cmd窗口，转到lib.exe所在文件夹下。输入命令：lib sqlite3.obj。这时会生成静态的sqlite3.lib（大小为2.91MB）如果无法生成，可以试试用管理员权限运行cmd。
- 将sqlite3.lib和sqlite3.h添加到VS工程就可以使用sqlite啦。
SQLite C/C++ Tutorial
C/C++ Interface APIs
介绍三个主要的 API，知道这三个API就可以简单的使用sqlite3了。原tutotial写得非常清楚，我直接复制过来了。
-
sqlite3_open(const char *filename, sqlite3 **ppDb)
This routine opens a connection to an SQLite database file and returns a database connection object to be used by other SQLite routines.
If the filename argument is NULL or ‘:memory:’, sqlite3_open() will create an in-memory database in RAM that lasts only for the duration of the session.
If filename is not NULL, sqlite3_open() attempts to open the database file by using its value. If no file by that name exists, sqlite3_open() will open a new database file by that name.
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sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)
This routine provides a quick, easy way to execute SQL commands provided by sql argument which can consist of more than one SQL command.
Here, first argument sqlite3 is open database object, sqlite_callback is a call back for which data is the 1st argument and errmsg will be return to capture any error raised by the routine.
-
sqlite3_close(sqlite3*)
This routine closes a database connection previously opened by a call to sqlite3_open(). All prepared statements associated with the connection should be finalized prior to closing the connection.
If any queries remain that have not been finalized, sqlite3_close() will return SQLITE_BUSY with the error message Unable to close due to unfinalized statements.
Connecting To Database
Following C code segment shows how to connect to an existing database. If database does not exist, then it will be created and finally a database object will be returned.
#include <stdio.h>
#include <sqlite3.h>
int main(int argc, char* argv[])
{
sqlite3 *db;
char *zErrMsg = 0;
int rc;
rc = sqlite3_open("test.db", &db);
if( rc ){
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
return(0);
}else{
fprintf(stderr, "Opened database successfully\n");
}
sqlite3_close(db);
}Now, let’s compile and run above program to create our database test.db in the current directory. You can change your path as per your requirement.
$gcc test.c -l sqlite3
$./a.out
Opened database successfully
If you are going to use C++ source code, then you can compile your code as follows:
$g++ test.c -l sqlite3
Here we are linking our program with sqlite3 library to provide required functions to C program. This will create a database file test.db in your directory and you will have the result something as follows:
-rwxr-xr-x. 1 root root 7383 May 8 02:06 a.out
-rw-r–r–. 1 root root 323 May 8 02:05 test.c
-rw-r–r–. 1 root root 0 May 8 02:06 test.db
Create a Table
Following C code segment will be used to create a table in previously created database:
#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));
return(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;
}When above program is compiled and executed, it will create COMPANY table in your test.db and final listing of the file will be as follows:
-rwxr-xr-x. 1 root root 9567 May 8 02:31 a.out
-rw-r–r–. 1 root root 1207 May 8 02:31 test.c
-rw-r–r–. 1 root root 3072 May 8 02:31 test.db
INSERT Operation
Following C code segment shows how we can create records in our COMPANY table created in above example:
#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));
return(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;
}When above program is compiled and executed, it will create given records in COMPANY table and will display following two line:
Opened database successfully
Records created successfully
SELECT Operation
Before we proceed with actual example to fetch records, let me give a little detail about the callback function, which we are using in our examples. This callback provides a way to obtain results from SELECT statements. It has the following declaration:
typedef int (*sqlite3_callback)(
void*, /* Data provided in the 4th argument of sqlite3_exec() */
int, /* The number of columns in row */
char**, /* An array of strings representing fields in the row */
char** /* An array of strings representing column names */
);If above callback is provided in sqlite_exec() routine as the third argument, SQLite will call the this callback function for each record processed in each SELECT statement executed within the SQL argument.
Following C code segment shows how we can fetch and display records from our COMPANY table created in above example:
#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));
return(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;
}When above program is compiled and executed, it will produce the following result:
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 Operation
Following C code segment shows how we can use UPDATE statement to update any record and then fetch and display updated records from our COMPANY table:
#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));
return(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;
}When above program is compiled and executed, it will produce the following result:
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 25000.0Callback 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
DELETE Operation
Following C code segment shows how we can use DELETE statement to delete any record and then fetch and display remaining records from our COMPANY table:
#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));
return(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;
}When above program is compiled and executed, it will produce the following result:
Opened database successfully
Callback function called: ID = 1
NAME = Paul
AGE = 32
ADDRESS = California
SALARY = 20000.0Callback 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