C语言实现sqlite3数据库查询的基本方法
sqlite回传函数相关 说了3种基本方法：callback，gettable和预处理stmt方法
下面给出测试代码和测试用数据库，代码如下
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "sqlite3.h"
//
//typedef int (*sqlite3_callback)(
// void* data, /* Data provided in the 4th argument of sqlite3_exec() */
// int ncols, /* The number of columns in row */
// char** values, /* An array of strings representing fields in the row */
// char** headers /* An array of strings representing column names */
//);
int callback(void* data, int ncols, char** values, char** headers)
{
int i;
int len =0;
int ll=0;
for(i=0; i < ncols; i++)
{
if(strlen(headers[i])>len)
len = strlen(headers[i]);
}
for(i=0; i < ncols; i++)
{
ll = len-strlen(headers[i]);
while(ll)
{
fprintf(stdout," ");
--ll;
}
fprintf(stdout, "%s: %s\n", headers[i], values[i]);
}
fprintf(stdout, "\n");
return 0;
}
int search_by_callback(const char* db_name, const char* sql_cmd)
{
int i = 0 ;
int j = 0 ;
int nrow = 0, ncolumn = 0;
char **azResult; //二维数组存放结果
sqlite3 *db=NULL;
char *zErrMsg = 0;
int rc;
int len=0;
if(access(db_name, 0) == -1)
{
fprintf(stderr, "%s not found\n", db_name);
return -1;
}
rc = sqlite3_open(db_name, &db);
if( rc != SQLITE_OK)
{
fprintf(stderr, "%s open failed: %s\n", db_name,sqlite3_errmsg(db));
sqlite3_close(db);
return -1;
}
//查询数据
rc = sqlite3_exec( db,sql_cmd, callback, NULL, &zErrMsg );
if( rc != SQLITE_OK)
{
fprintf(stderr, "%s %s: %s\n", db_name,sql_cmd, sqlite3_errmsg(db));
if(zErrMsg)
{
fprintf(stderr,"ErrMsg = %s \n", zErrMsg);
sqlite3_free(zErrMsg);
}
sqlite3_close(db);
return -1;
}
if(zErrMsg)
{
sqlite3_free(zErrMsg);
}
//关闭数据库
sqlite3_close(db);
return 0;
}
int search_by_table(const char* db_name, const char* sql_cmd)
{
int i = 0 ;
int j = 0 ;
int nrow = 0, ncolumn = 0;
char **azResult; //二维数组存放结果
sqlite3 *db=NULL;
char *zErrMsg = 0;
int rc;
int len=0;
if(access(db_name, 0) == -1)
{
fprintf(stderr, "%s not found\n", db_name);
return -1;
}
rc = sqlite3_open(db_name, &db);
if( rc != SQLITE_OK)
{
fprintf(stderr, "%s open failed: %s\n", db_name,sqlite3_errmsg(db));
sqlite3_close(db);
return -1;
}
//查询数据
rc = sqlite3_get_table( db , sql_cmd, &azResult , &nrow , &ncolumn , &zErrMsg );
if( rc != SQLITE_OK)
{
fprintf(stderr, "%s %s: %s\n", db_name,sql_cmd, sqlite3_errmsg(db));
if(zErrMsg)
fprintf(stderr,"ErrMsg = %s \n", zErrMsg);
sqlite3_free_table( azResult );
sqlite3_close(db);
return -1;
}
for(j=0; j < ncolumn; j++)
{
if(strlen(azResult[j])>len)
len = strlen(azResult[j]);
}
//从第0索引到第 nColumn - 1索引都是字段名称
//从第 nColumn 索引开始，后面都是字段值
for( i = 0 ; i < nrow; i++ )
{
for(j=0; j < ncolumn; j++)
{
int ll = (len- strlen(azResult[j]));
while(ll)
{
printf(" ");
--ll;
}
printf( "%s: %s\n", azResult[j], azResult[(i+1)*ncolumn+j]);
}
printf("\n");
}
#if 0
for( j = 0 ; j < ncolumn; j++ )
{
printf( "%s ", azResult[j]);
}
printf( "\n");
for( i=ncolumn ; i<( nrow + 1 ) * ncolumn ; i++ )
{
if(((i-ncolumn+1)%ncolumn) ==0)
printf( "%s\n",azResult[i]);
else
printf( "%s ",azResult[i] );
}
#endif
//与sqlite3_get_table对应，释放掉 azResult 的内存空间
sqlite3_free_table( azResult );
//关闭数据库
sqlite3_close(db);
return 0;
}
int search_by_stmt(const char* db_name, const char* sql_cmd)
{
sqlite3 *db=NULL;
sqlite3_stmt* stmt = 0;
int ncolumn = 0;
const char *column_name;
int vtype , i;
int rc;
if(access(db_name, 0) == -1)
{
fprintf(stderr, "%s not found\n", db_name);
return -1;
}
rc = sqlite3_open(db_name, &db);
if( rc != SQLITE_OK)
{
fprintf(stderr, "%s open failed: %s\n", db_name,sqlite3_errmsg(db));
sqlite3_close(db);
return -1;
}
//查询数据
rc = sqlite3_prepare_v2(db, sql_cmd, -1, &stmt, 0);
if (rc != SQLITE_OK)
{
fprintf(stderr, "%s %s: %s\n", db_name,sql_cmd, sqlite3_errmsg(db));
sqlite3_close(db);
return -1;
}
ncolumn = sqlite3_column_count(stmt);
while (sqlite3_step(stmt) == SQLITE_ROW)
{
for(i = 0 ; i < ncolumn ; i++ )
{
vtype = sqlite3_column_type(stmt , i);
column_name = sqlite3_column_name(stmt , i);
switch( vtype )
{
case SQLITE_NULL:
fprintf(stdout, "%s: null\n", column_name);
break;
case SQLITE_INTEGER:
fprintf(stdout, "%s: %d\n", column_name,sqlite3_column_int(stmt,i));
break;
case SQLITE_FLOAT:
fprintf(stdout, "%s: %f\n", column_name,sqlite3_column_double(stmt,i));
break;
case SQLITE_BLOB: /* arguably fall through... */
fprintf(stdout, "%s: BLOB\n", column_name);
break;
case SQLITE_TEXT:
fprintf(stdout, "%s: %s\n", column_name,sqlite3_column_text(stmt,i));
break;
default:
fprintf(stdout, "%s: ERROR [%s]\n", column_name, sqlite3_errmsg(db));
break;
}
}
}
sqlite3_finalize(stmt);
//关闭数据库
sqlite3_close(db);
return 0;
}
int main(int argc, char* argv[])
{
int i=0;
if(argc != 4)
{
fprintf(stderr, "usage: %s [table/callback/stmt] <db_name> <sql_cmd>\r\n", argv[0]);
return -1;
}
if((strcmp(argv[1],"table") ==0))
search_by_table(argv[2],argv[3]);
else if((strcmp(argv[1],"callback") ==0))
search_by_callback(argv[2],argv[3]);
else
search_by_stmt(argv[2],argv[3]);
return 0;
}
编译 gcc sqlite3_search.c sqlite3.c -o sqlite3_search -lpthread -ldl
测试
./sqlite3_search callback KTV.sqlite "SELECT id,name FROM OVT_SONG where SONG_STAR =鄭秀文'"
./sqlite3_search table KTV.sqlite "SELECT id,name FROM OVT_SONG where SONG_STAR =鄭秀文'"
./sqlite3_search stmt KTV.sqlite "SELECT id,name FROM OVT_SONG where SONG_STAR =鄭秀文'"
数据库文件下载地址 KTV.sqlite