[gameprogrammer] sqlite example program
- From: Chris Nystrom <cnystrom@xxxxxxxxx>
- To: gameprogrammer@xxxxxxxxxxxxx
- Date: Sat, 22 May 2010 00:56:59 -0500
Below is an example c program that I wrote to use the SQLite library
(http://www.sqlite.org/). It compiles without error under Linux.
SQLite seems to be far more trouble to use than simply creating
arrays. I assume that as you scale up though, it is important for
performance to have an actual database instead of internal arrays of
data. Is there a rule of thumb about when you should use a database?
Or is there some other reason to use SQL besides performance with
large systems?
Chris
--
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
sqlite3 *db;
void open_db(char *db_name)
{
if (sqlite3_open(db_name, &db)) {
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
sqlite3_close(db);
}
}
char **result;
int nrow = 0;
int ncol = 0;
int db_exe(char *s_exe)
{
int rc;
char *zErrMsg = 0;
rc = sqlite3_get_table(db, /* An open database */
s_exe, /* SQL to be executed */
&result, /* Result written to a char *[] */
&nrow, /* Number of result rows */
&ncol, /* Number of result columns */
&zErrMsg /* Error msg written here */
);
return rc;
}
void db_close(void)
{
sqlite3_close(db);
}
void get_data(void)
{
int i, j;
if (nrow > 0) {
printf("nrow = %d\n", nrow);
printf("ncol = %d\n\n", ncol);
/* header */
for (i = 0; i < ncol; ++i)
printf("%s\t", result[i]);
printf("\n");
/* data rows */
for (i = 0; i < nrow; i++) {
for (j = 0; j < ncol; j++) {
printf("%s\t", result[(ncol * (i + 1)) + j]);
}
printf("\n");
}
}
sqlite3_free_table(result);
}
int main(int argc, char **argv)
{
char *db_name = "test.db";
/* remove old db if it exists */
remove(db_name);
/* create db */
open_db(db_name);
/* create emp table */
db_exe("create table emp (name varchar(15),age int,weight double)");
/* insert data into tables */
db_exe("insert into emp (name,age,weight) values ('Bob',47,172)");
db_exe("insert into emp (name,age,weight) values ('Sue',38,134)");
/* show data in emp table */
db_exe("select * from emp");
get_data();
return 0;
}
--
E-Mail: Chris Nystrom <cnystrom@xxxxxxxxx>
Saving the world from web programming.
http://www.newio.org - G-Talk: cnystrom
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