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: %sn",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 foundn",db_name);  
		return -1;  
	}
	
	rc = sqlite3_open(db_name,&db);

	if( rc != SQLITE_OK)
	{  
		fprintf(stderr,"%s open failed: %sn",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: %sn",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,sqlite3_errmsg(db));  
		sqlite3_close(db);  
		return -1;  
	}  

	//查询数据  
	rc = sqlite3_get_table( db,&azResult,&nrow,&ncolumn,&zErrMsg );  
	if( rc != SQLITE_OK)
	{  
		fprintf(stderr,sqlite3_errmsg(db));  
		if(zErrMsg)
			fprintf(stderr,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: %sn",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( "%sn",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,sqlite3_errmsg(db));  
		sqlite3_close(db);  
		return -1;  
	}  

	//查询数据  
	rc = sqlite3_prepare_v2(db,-1,&stmt,0);
	if (rc != SQLITE_OK)
	{
		fprintf(stderr,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: nulln",column_name);	
				break;
			  case SQLITE_INTEGER:
				  fprintf(stdout,"%s: %dn",column_name,sqlite3_column_int(stmt,i));	
				break;
			  case SQLITE_FLOAT:
				  fprintf(stdout,"%s: %fn",sqlite3_column_double(stmt,i));	
				break;
			  case SQLITE_BLOB: /* arguably fall through... */
				  fprintf(stdout,"%s: BLOBn",column_name);	
				break;
			  case SQLITE_TEXT: 
				  fprintf(stdout,sqlite3_column_text(stmt,i));	
				break;
			  default:
				  fprintf(stdout,"%s: ERROR [%s]n",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>rn",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_searchtable KTV.sqlite "SELECT id,name FROM OVT_SONG where SONG_STAR =鄭秀文'"
./sqlite3_searchstmtKTV.sqlite "SELECT id,name FROM OVT_SONG where SONG_STAR =鄭秀文'"

数据库文件下载地址 KTV.sqlite

（编辑：李大同）

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