SQLite3 BLOB增删改查编写
SQLite 是一个软件库，实现了自给自足的、无服务器的、零配置的、事务性的SQL数据库引擎。SQLite是在世界上最广泛部署的SQL数据库引擎。SQLite源代码不受版权限制。
SQLite3安装及配置
在Ubuntu中，使用下面命令可以快速安装上手SQLite3：
sudo apt-get install sqlite3
sudo apt-get install libsqlite3-dev在编译嵌入式Linux执行程序时，如果文件系统不支持SQLite命令，则需要找到交叉编译工具或者厂商提供的库文件，同时在项目文件和目标文件系统中添加链接。
SQLite3可视化工具：下载
SQLite3常用命令
C/SQLite3基本操作
SQLite3 BLOB数据格式
BLOB是一种根据输入自定的数据格式，允许一次存储大量数据，与TEXT格式相比，更加SQLite3会对TEXT进行转换，而不会对BLOB数据格式有任何修改。因此BLOB适用于数据帧存储。
例如要建立一个历史遥测的数据库：
id time_stamp data
---------- ---------- ------------
1 14569 825400668368
2 14569 277172517040
3 14570 143753724361我们定义一个消息结构体：
/* Massege record in the database*/
typedef struct
{
int id; //column id;
uint64_t time_stamp; //column time_stamp
uint8_t buf[MAX_DATA_BUFFER_SIZE]; //buf in column blob
int buf_len; //length of buf in blob
} db_data;使用下面sqldev.c中的函数可以完成增删改查的操作：
- 插入新的记录
db_add_data(db, "delayed_tlm", msg);
如果记录已经有则会覆盖，如果超出ID允许的最大值，则会从1开始重新写入 - 根据ID删除记录
db_delete_blob_by_id(db, "delayed_tlm", id) - 查找ID的记录是否存在
db_judge_id_exist(db, "delayed_tlm", id); - 查找最新记录的ID和时间
db_get_max_time_stamp_id() and then call db_get_blob_by_id() to get the data - 根据ID和时间查找记录
db_get_blob_by_id() or db_get_blob_by_ts() - 修改某条记录的BLOB值
db_write_blob_by_id()不会更改时间的值
db_add_data()会刷新这条记录的所有变量
sqldev.h
/************************************************************************************
* Copyright (C), 2011-2021, Micro-Satellite Research Center, Zhejiang University
*************************************************************************************
* File Name: sqldev.h
* Project: Sqlite3 API definition for ZHX CES
* Group: CES
* Author: Jianliang Shen
* Creation Date: June-19-2020
* Description:
SQLite3 function and val definition
* Revision:
June-18-2020 : Create
June-19-2020 : Release 0.10
*************************************************************************************/
#ifndef __SQLDEV_H__
#define __SQLDEV_H__
/************************************************************************************
dataTele.db--
| |-id
|--rt_tlm--|-time_stamp
| |-data
| |-id
|--delayed_tlm--|-time_stamp
| |-data
| |-id
|--tlc--|-time_stamp
| |-data
e.g. select * from delayed_tlm:
id time_stamp data
---------- ---------- ------------
1 14569 825400668368
2 14569 277172517040
3 14570 143753724361
...
************************************************************************************/
#include "am57xx.h"
#include "sqlite3.h"
#define MAX_DATA_BUFFER_SIZE 1024 //MAX buf size in blob
#define MAX_ID 30 //MAX msg record numbers in the databse
/* Massege record in the database*/
typedef struct
{
int id; //column id;
uint64_t time_stamp; //column time_stamp
uint8_t buf[MAX_DATA_BUFFER_SIZE]; //buf in column blob
int buf_len; //length of buf in blob
} db_data;
#define DATABASE_PATH "dataTele.db" //database path
#define TABLE_RT_TLM "rt_tlm" //real time telemetry
#define TABLE_DELAYED_TLM "delayed_tlm" //delayed telemetry
#define TABLE_TLC "tlc" //telecontrol
#define DEBUG_SWITCH 0 //switch to debug
#define TABLE_NOT_EXIST 1 //whether the tables exist
#define COL_ID 1
#define COL_TS 2
#define COL_DATA 3
#define SQL_CREATE_TABLE "CREATE TABLE IF NOT EXISTS %s(id INTEGER PRIMARY KEY, time_stamp BIGINT, data BLOB);"
#define SQL_INSERT_DATA "REPLACE INTO %s(id, time_stamp, data) VALUES(?, ?, ?)"
#define SQL_QUIERY_TIME_STAMP_BY_ID "SELECT id,time_stamp FROM %s WHERE ID = %d"
#define SQL_QUIERY_BY_ID "SELECT rowid, * FROM %s WHERE id = ?"
#define SQL_QUIERY_BY_TIME_STAMP "SELECT rowid, * FROM %s WHERE time_stamp = ?"
#define SQL_QUIERY_ID_BY_MAX_TIME_STAMP "SELECT id,time_stamp FROM %s " \
"WHERE time_stamp=(SELECT MAX(time_stamp) FROM %s)"
#define SQL_DELETE_BY_ID "DELETE from %s where ID= %d; "
sqlite3 *db_open(char *filename);
void db_close(sqlite3 *db);
int db_blob_read(sqlite3 *db, char *tab_name, int rowid, void *data_buf, int buf_len);
int db_add_data(sqlite3 *db, char *tab_name, db_data *msg);
int db_get_blob_by_id(sqlite3 *db, char *tab_name, db_data *msg);
int db_get_blob_by_ts(sqlite3 *db, char *tab_name, db_data *msg);
int db_get_max_time_stamp_id(sqlite3 *db, char *tab_name, uint64_t *time_stamp);
int db_get_time_stamp_by_id(sqlite3 *db, char *tab_name, int id, uint64_t *time_stamp);
int db_judge_id_exist(sqlite3 *db, char *tab_name, int id);
int db_write_blob_by_id(sqlite3 *db, char *tab_name, int id, uint8_t *data, int len);
int delete_blob_by_id(sqlite3 *db, char *tab_name, int id);
void show_msg(db_data *msg);
#endifsqldev.c
/************************************************************************************
* Copyright (C), 2011-2021, Micro-Satellite Research Center, Zhejiang University
*************************************************************************************
* File Name: sqldev.c
* Project: Sqlite3 API support for ZHX CES
* Group: CES
* Author: Jianliang Shen
* Creation Date: June-19-2020
* Description:
SQLite3 Add/Delete/Search/Change
Assume there is a pointer to the sqlite3 file named *db which has a table called
delayed_tlm. The database struct can be find in sqldev.h
1. When you want to add a msg into the table:
e.g. db_add_data(db, "delayed_tlm", msg);
NOTE that this function will update the whole msg if the msg has been established!
2. When you want to delete a msg in the table by id:
e.g. db_delete_blob_by_id(db, "delayed_tlm", id)
3. When you want to check if msg of id exist:
e.g. db_judge_id_exist(db, "delayed_tlm", id);
4. When you want to get the newst msg:
e.g. db_get_max_time_stamp_id() and then call db_get_blob_by_id() to get the data
5. When you want to search and read data from the table:
e.g. db_get_blob_by_id() or db_get_blob_by_ts()
6. When you want to change msg in the table:
e.g. db_write_blob_by_id() CAN ONLY used if the msg has been established.
NOTE that the time_stamp will NOT be changed.
db_add_data() NOTE that this function will update the whole msg if
the msg has been established!
* Revision:
June-18-2020 : Create
June-19-2020 : Release 0.10
*************************************************************************************/
#include "base/devices/sqldev.h"
#include "global.h"
// ----------------------------------------
// \brief: This function is used to open databse in filepath ,if the database does NOT exist, it will create a new one and initialize new tables.
// \param: char *filepath
// \return: sqlite3 *db: sqlite3 poniter to the database
// ----------------------------------------
sqlite3 *db_open(char *filepath)
{
sqlite3 *db;
int rc, rm, rd;
char cmd[1000];
rc = sqlite3_open(filepath, &db);
if (rc)
{
dbg("Can't open database: %s\n", sqlite3_errmsg(db));
sqlite3_close(db);
return NULL;
}
//initialize the table TABLE_TLC and TABLE_RT_TLM and TABLE_DELAYED_TLM in database if databse doesn't exist.
//the cmd is formatted to create table, here create three tables
sprintf(cmd, SQL_CREATE_TABLE, TABLE_TLC);
rc = sqlite3_exec(db, cmd, 0, 0, 0);
sprintf(cmd, SQL_CREATE_TABLE, TABLE_RT_TLM);
rm = sqlite3_exec(db, cmd, 0, 0, 0);
sprintf(cmd, SQL_CREATE_TABLE, TABLE_DELAYED_TLM);
rd = sqlite3_exec(db, cmd, 0, 0, 0);
if (rc != SQLITE_OK || rm != SQLITE_OK || rd != SQLITE_OK)
{
sqlite3_close(db);
return NULL;
}
return db;
}
// ----------------------------------------
// \brief: This function is used to close databse in filepath.
// \param: sqlite3 *db: sqlite3 pointer to be closed.
// \return: NULL
// ----------------------------------------
void db_close(sqlite3 *db)
{
sqlite3_close(db);
}
// ----------------------------------------
// \brief: This function is used to read blob data from appointed table to data_buf. The "buf_len" will update to the actual data length in blob.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to read blob.
// \param: int rowid : SELECT zColumn FROM zDb.zTable WHERE [rowid] = iRow.
// \param: void *data_buf : buf to store blob data.
// \param: int buf_len : if you don't know the blob_length, you should set MAXSIZE
// \return: length of blob length.
// ----------------------------------------
int db_blob_read(sqlite3 *db, char *tab_name, int rowid, void *data_buf, int buf_len)
{
sqlite3_blob *blob = NULL;
int blob_length = 0;
int rc = -1;
rc = sqlite3_blob_open(db, "main", tab_name, "data", rowid, 0, &blob);
if (rc != SQLITE_OK)
{
dbg("Failed to open BLOB: %s\n", sqlite3_errmsg(db));
return -1;
}
blob_length = sqlite3_blob_bytes(blob);
if (blob_length > buf_len)
{
dbg("Invalid buffer length\n");
sqlite3_blob_close(blob);
return -1;
}
rc = sqlite3_blob_read(blob, data_buf, blob_length, 0);
if (rc != SQLITE_OK)
{
dbg("Failed to read BLOB: %s\n", sqlite3_errmsg(db));
sqlite3_blob_close(blob);
return -1;
}
sqlite3_blob_close(blob);
return blob_length;
}
// ----------------------------------------
// \brief: This function is used to add massege into appointed table in database. NOTE: If the msg has been established, it will update the msg.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to add massege.
// \param: db_data *msg : msg pointer.
// \return: 0 if success. -1 if failed.
// ----------------------------------------
int db_add_data(sqlite3 *db, char *tab_name, db_data *msg)
{
CHECK_POINTER(msg);
sqlite3_stmt *stmt = NULL;
char cmd[1000];
int rc = -1;
if (msg->id == -1)
{
msg->id = (int)sqlite3_last_insert_rowid(db) + 1;
}
if (msg->id > MAX_ID) //LOOP write
{
msg->id = 1;
}
sprintf(cmd, SQL_INSERT_DATA, tab_name);
rc = sqlite3_prepare_v2(db, cmd, -1, &stmt, NULL); //get Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Prepare failed: %s\n", sqlite3_errmsg(db));
return -1;
}
rc = sqlite3_bind_int(stmt, COL_ID, msg->id); //add id
if (rc != SQLITE_OK)
{
dbg("Bind failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
rc = sqlite3_bind_int64(stmt, COL_TS, msg->time_stamp); //add time_stamp
if (rc != SQLITE_OK)
{
dbg("Bind failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
rc = sqlite3_bind_blob(stmt, COL_DATA, msg->buf, msg->buf_len, SQLITE_STATIC); //add blob
if (rc != SQLITE_OK)
{
dbg("Bind failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
rc = sqlite3_step(stmt);
if (rc != SQLITE_DONE)
{
dbg("Step failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
sqlite3_finalize(stmt);
return 0;
}
// ----------------------------------------
// \brief: This function is used to read blob data by id. NOTE: If the id doesn't exist, the msg->buf_len = 0.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to search.
// \param: db_data *msg : msg pointer.
// \return: msg->buf_len if success. -1 or 0 if failed.
// ----------------------------------------
int db_get_blob_by_id(sqlite3 *db, char *tab_name, db_data *msg)
{
CHECK_POINTER(msg);
if (db_judge_id_exist(db, tab_name, msg->id) < 0) //id NOT EXISTS
{
msg->buf_len = 0;
return 0;
}
sqlite3_stmt *stmt = NULL;
sqlite_int64 rowid = 0;
int rc = -1;
char cmd[1000];
sprintf(cmd, SQL_QUIERY_BY_ID, tab_name);
rc = sqlite3_prepare_v2(db, cmd, -1, &stmt, 0); //get Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Prepare failed: %s\n", sqlite3_errmsg(db));
return -1;
}
rc = sqlite3_bind_int(stmt, COL_ID, msg->id); //bind Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Bind failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
rc = sqlite3_step(stmt);
if (rc == SQLITE_ROW)
{
rowid = sqlite3_column_int64(stmt, 0); //get rowid
}
else if (rc == SQLITE_DONE)
{
sqlite3_finalize(stmt); //NO data
return 0;
}
else
{
dbg("Step error: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
sqlite3_finalize(stmt);
/*read blob in Prepared Statement Object */
msg->buf_len = db_blob_read(db, tab_name, rowid, msg->buf, msg->buf_len);
return msg->buf_len;
}
// ----------------------------------------
// \brief: This function is used to read blob data by TS.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to search.
// \param: db_data *msg : msg pointer.
// \return: msg->buf_len if success. -1 or 0 if failed.
// ----------------------------------------
int db_get_blob_by_ts(sqlite3 *db, char *tab_name, db_data *msg)
{
sqlite3_stmt *stmt = NULL;
sqlite_int64 rowid = 0;
int rc = -1;
char cmd[1000];
sprintf(cmd, SQL_QUIERY_BY_TIME_STAMP, tab_name);
rc = sqlite3_prepare_v2(db, cmd, -1, &stmt, 0); //get Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Prepare failed: %s\n", sqlite3_errmsg(db));
return -1;
}
rc = sqlite3_bind_int64(stmt, 1, msg->time_stamp); //bind Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Bind failed: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
rc = sqlite3_step(stmt);
if (rc == SQLITE_ROW)
{
rowid = sqlite3_column_int64(stmt, 0); //get rowid
}
else if (rc == SQLITE_DONE)
{
sqlite3_finalize(stmt);
return 0;
}
else
{
dbg("Step error: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
sqlite3_finalize(stmt);
/*read blob in Prepared Statement Object */
msg->buf_len = db_blob_read(db, tab_name, rowid, msg->buf, msg->buf_len);
return msg->buf_len;
}
// ----------------------------------------
// \brief: This function is used to get the newst msg.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to search.
// \param: uint64_t *time_stamp : time_stamp pointer.
// \return: id if success. -1 or 0 if failed.
// ----------------------------------------
int db_get_max_time_stamp_id(sqlite3 *db, char *tab_name, uint64_t *time_stamp)
{
sqlite3_stmt *stmt = NULL;
int id = -1;
int rc = -1;
char cmd[1000];
sprintf(cmd, SQL_QUIERY_ID_BY_MAX_TIME_STAMP, tab_name, tab_name);
rc = sqlite3_prepare_v2(db, cmd, -1, &stmt, 0); //get Prepared Statement Object
if (rc != SQLITE_OK)
{
dbg("Prepare failed: %s\n", sqlite3_errmsg(db));
return -1;
}
rc = sqlite3_step(stmt);
if (rc == SQLITE_ROW)
{
id = sqlite3_column_int(stmt, 0);
if (time_stamp)
{
*time_stamp = sqlite3_column_int64(stmt, 1); //get time_stamp
}
}
else if (rc == SQLITE_DONE)
{
id = 0;
if (time_stamp)
{
*time_stamp = 0;
}
}
else
{
dbg("Step error: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
sqlite3_finalize(stmt);
return id;
}
// ----------------------------------------
// \brief: This function is used to get time_stamp by id.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to add massege.
// \param: int id : which id
// \param: uint64_t *time_stamp : pointer to time_stamp
// \return: 0 if success. -1 if failed.
// ----------------------------------------
int db_get_time_stamp_by_id(sqlite3 *db, char *tab_name, int id, uint64_t *time_stamp)
{
sqlite3_stmt *stmt = NULL;
int rc = -1;
char cmd[1000];
sprintf(cmd, SQL_QUIERY_TIME_STAMP_BY_ID, tab_name, id);
rc = sqlite3_prepare_v2(db, cmd, -1, &stmt, 0);
if (rc != SQLITE_OK)
{
dbg("Prepare failed: %s\n", sqlite3_errmsg(db));
return -1;
}
rc = sqlite3_step(stmt);
if (rc == SQLITE_ROW)
{
id = sqlite3_column_int(stmt, 0);
if (time_stamp)
{
*time_stamp = sqlite3_column_int64(stmt, 1);
}
}
else if (rc == SQLITE_DONE)
{
id = 0;
if (time_stamp)
{
*time_stamp = 0;
}
}
else
{
dbg("Step error: %s\n", sqlite3_errmsg(db));
sqlite3_finalize(stmt);
return -1;
}
sqlite3_finalize(stmt);
return 0;
}
// ----------------------------------------
// \brief: This function is used to judge the id whether exist.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to search.
// \param: int id : id
// \return: 0 if exist. -1 if NOT exist.
// ----------------------------------------
int db_judge_id_exist(sqlite3 *db, char *tab_name, int id)
{
uint64_t time_stamp;
db_get_time_stamp_by_id(db, tab_name, id, &time_stamp);
return time_stamp > 0 ? 0 : -1;
}
// ----------------------------------------
// \brief: This function is used to write blob data by id. NOTE: the time_stamp will not change.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to add massege.
// \param: int id : id
// \param: uint8_t *data : data
// \param: int len : data len
// \return: 0 if success. -1 if msg doesn't exist.
// ----------------------------------------
int db_write_blob_by_id(sqlite3 *db, char *tab_name, int id, uint8_t *data, int len)
{
if (db_judge_id_exist(db, tab_name, id) < 0)
{
return -1;
}
sqlite3_stmt *stmt = NULL;
char cmd[1000];
int rc = -1;
uint64_t tmp_time_stamp; //get the old time_stamp
db_get_time_stamp_by_id(db, tab_name, id, &tmp_time_stamp);
db_data *msg = (db_data *)malloc(sizeof(db_data));
msg->id = id;
msg->time_stamp = tmp_time_stamp;
msg->buf_len = len;
memcpy(msg->buf, data, msg->buf_len);
db_add_data(db, tab_name, msg); //update the blob
free(msg);
return 0;
}
// ----------------------------------------
// \brief: This function is used to delete msg by id.
// \param: sqlite3 *db : sqlite3 pointer.
// \param: char *tab_name : which table to delete.
// \param: int id : msg id
// \return: 0 if success. -1 if failed.
// ----------------------------------------
int delete_blob_by_id(sqlite3 *db, char *tab_name, int id)
{
if (db_judge_id_exist(db, tab_name, id) < 0)
{
return 0;
}
char *zErrMsg = 0;
int rc;
char cmd[1000];
/* Create merged SQL statement */
sprintf(cmd, SQL_DELETE_BY_ID, tab_name, id);
/* Execute SQL statement */
rc = sqlite3_exec(db, cmd, NULL, NULL, &zErrMsg);
if (rc != SQLITE_OK)
{
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
return -1;
}
else
{
return 0;
}
}
// ----------------------------------------
// \brief: This function is used to show blob in msg.
// \param: db_data *msg: msg pointer.
// \return: NULL
// ----------------------------------------
void show_msg(db_data *msg)
{
printf("blob = \n");
for (int i = 1; i < msg->buf_len + 1; i++)
{
printf("0x%02x ", msg->buf[i - 1]);
if (i % 32 == 0)
{
printf("\n");
}
}
printf("\n");
}test.c
void sql_test()
{
sqlite3 *db = db_open(DATABASE_PATH);
#if TABLE_NOT_EXIST
for (int i = 1; i <= MAX_ID; i++)
{
delete_blob_by_id(db, TABLE_DELAYED_TLM, i);
}
#endif
#if TABLE_NOT_EXIST
time_t seed = time(NULL);
srand(seed);
db_data *msg = (db_data *)malloc(sizeof(db_data));
msg->id = 0;
uint8_t data[256];
for (int i = 0; i < 50; i++)
{
for (int i = 0; i < 256; i++)
{
data[i] = (uint8_t)(rand() % 10 + 48);
}
msg->id++;
msg->time_stamp = time(NULL);
msg->buf_len = sizeof(data);
memcpy(msg->buf, data, msg->buf_len);
db_add_data(db, TABLE_DELAYED_TLM, msg);
usleep(100000);
}
free(msg);
#endif
//get the max time msg id and time_stamp
uint64_t max_time;
int max_time_id = db_get_max_time_stamp_id(db, TABLE_DELAYED_TLM, &max_time);
printf("max_time_id = %d, max_time = %ld\n", max_time_id, max_time);
//get the msg of max time_stamp by function "db_get_blob_by_ts"
db_data *max_tm_msg = (db_data *)malloc(sizeof(db_data));
max_tm_msg->time_stamp = max_time;
max_tm_msg->buf_len = MAX_DATA_BUFFER_SIZE;
db_get_blob_by_ts(db, TABLE_DELAYED_TLM, max_tm_msg);
show_msg(max_tm_msg);
free(max_tm_msg);
//update blob data by id, the time will be updated
// uint8_t buf[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
// db_data *msg = (db_data *)malloc(sizeof(db_data));
// msg->id = 10;
// msg->time_stamp = time(NULL);
// msg->buf_len = sizeof(buf);
// memcpy(msg->buf, buf, msg->buf_len);
// db_add_data(db, TABLE_DELAYED_TLM, msg);
//update blob data by id, the time will NOT be updated
uint8_t buf[] = {0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30};
db_write_blob_by_id(db, TABLE_DELAYED_TLM, 10, buf, sizeof(buf));
//
delete_blob_by_id(db, TABLE_DELAYED_TLM, 15);
int ret = db_judge_id_exist(db, TABLE_DELAYED_TLM, 15);
if (ret < 0)
{
printf("cannot find id = 15 msg\n");
}
delete_blob_by_id(db, TABLE_DELAYED_TLM, 15);
// read blob from table by id
db_data *ret_msg = (db_data *)malloc(sizeof(db_data));
ret_msg->id = 15;
ret_msg->buf_len = MAX_DATA_BUFFER_SIZE;
db_get_blob_by_id(db, TABLE_DELAYED_TLM, ret_msg);
show_msg(ret_msg);
free(ret_msg);
db_close(db);
}