I don't understand why this code shows me:
database table is locked
when I try to delete the *_old table. I use this code to change the type of a table column dynamically.
This is my code:
sqlite3_exec(this->connection, "BEGIN TRANSACTION;", NULL, NULL, NULL);
string query = "ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;";
cout << "8 " << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
query = "CREATE TABLE " + tableName + " (";
for(int i = 0; i < (int)colName.size(); i++)
{
query += colName.at(i) + " " + colType.at(i);
for(int j = 0; j < (int)primaryKey.size(); j++)
{
if(strcmp(colName.at(i).c_str(), primaryKey.at(j).c_str()) == 0)
{
query += " PRIMARY KEY ";
break;
}
}
query += " " + colParam.at(i);
if(i < ((int)colName.size() - 1))
query += ", ";
}
query += ");";
cout << "9" << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
query = "INSERT INTO " + tableName + " SELECT * FROM " + tableName + "_old;";
cout << "10" << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
query = "DROP TABLE " + tableName + "_old;";
cout << "11" << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
cout << sqlite3_errmsg(this->connection) << endl;
if(error > 0)
{
query = "ROLLBACK TRANSACTION;";
cout << "12" << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
}
else
{
query = "COMMIT TRANSACTION;";
cout << "13" << query << endl;
if(sqlite3_exec(this->connection, query.c_str(), NULL, NULL, NULL) != SQLITE_OK)
error = 1;
}
I solved, there was some previous queries with open statement, I use this code to close all before drop the table
sqlite3_stmt *stmt=0;
while((stmt=sqlite3_next_stmt(this->connection,0))!=0)
{
sqlite3_finalize(stmt);
}
Related
I am attempting to copy the same table schema and a select number of entries from my main database to a new secondary database. I am able to create the second database START.sql and inside it, a table called copied, however the schema between that and the main masterDatabaseTest differ and as a result I receive the error:
table START.copied has 1 columns but 5 values were supplied
The code:
void newLog(std::string tableName, std::string timeStart, std::string timeEnd)
{
char *err_msg = NULL;
int rc= -1;
std::string dbLogName = timeStart;
std::string dbLogName2 = dbLogName + ".sql";
std::string attachQuery = "ATTACH DATABASE 'START.sql' AS 'START';";
std::string copyTable = "CREATE TABLE START.copied AS SELECT sql FROM sqlite_master WHERE type='table' and name='masterDatabaseTest';";
std::string insertCopied = "INSERT INTO START.copied SELECT * from sqlite_master where type='table' and name='masterDatabaseTest';";
std::string detach = "DETACH DATABASE START;";
std::cout << dbLogName << "\n"
<< attachQuery << "\n"
<< copyTable << "\n"
<< insertCopied << "\n"
<< detach << std::endl;
sqlite3_exec(db, "BEGIN TRANSACTION;", NULL, NULL, 0);
rc = sqlite3_open(databaseName.c_str(), &db); // CREATES DATABASE
std::cout << "OPEN: " << rc << std::endl;
rc = sqlite3_exec(db, attachQuery.c_str(), NULL, 0, &err_msg);
std::cout << "ATTACH: " << rc << std::endl;
if(rc != 0){
std::cout << err_msg << std::endl;
}
rc = sqlite3_exec(db, copyTable.c_str(), NULL, 0, &err_msg);
std::cout << "copyTable: " << rc << std::endl;
if(rc != 0){
std::cout << err_msg << std::endl;
}
rc = sqlite3_exec(db, insertCopied.c_str(), NULL, 0, &err_msg);
std::cout << "insertCopied: " << rc << std::endl;
if(rc != 0){
std::cout << err_msg << std::endl;
}
rc = sqlite3_exec(db, detach.c_str(), NULL, 0, &err_msg);
std::cout << "detach: " << rc << std::endl;
if(rc != 0){
std::cout << err_msg << std::endl;
}
sqlite3_exec(db, "END TRANSACTION;", NULL, NULL, 0);
}
inside commandline sqlite3 database.sql:
sqlite> .schema
CREATE TABLE masterDatabaseTest (ID INTEGER,RECORDTIME BIGINT,TYPE INTEGER,TIMESTAMP BIGINT,ENCODER1 INTEGER,ENCODER2 INTEGER,ENCODER3 INTEGER,ENCODER4 INTEGER,ENCODER5 INTEGER);
inside commandline sqlite3 START.sql
sqlite> .schema
CREATE TABLE copied(sql TEXT);
If you want "an exact copy of the schema of masterDatabaseTest", you do not need to use sqlite_master. The DDL query
CREATE TABLE START.copied AS SELECT * from masterDatabaseTest
will accomplish that. If you want a select number of entries, add a WHERE clause. If you do not want any rows from the source table, add a WHERE 0; it will create the schema and will not select any rows.
I have figured out my problem :)
the db instance was not pointing to the correct database, so although I was able to execute it correctly in commandline, the actual program has no initialised the database connection so the sqlite3_exec command was pointing to nothing.
Fixing that I was able to execute the commands with no problem.
Here's my code
std::string dbFileName = "GalleryDB.sqlite";
int doesFileExist = _access(dbFileName.c_str(), 0);
int res = sqlite3_open(dbFileName.c_str(), &db);
if (res != SQLITE_OK) {
db = nullptr;
std::cout << "Failed to open DB" << std::endl;
return -1;
}
if (doesFileExist == 0) {
char* sqlStatement = "CREATE TABLE USERS (ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL , NAME TEXT NOT NULL);";
char** errMessage = nullptr;
res = sqlite3_exec(db, sqlStatement, nullptr, nullptr, errMessage);
if (res != SQLITE_OK)
{
std::cout << res;
std::cout << "ERROR! CANT CREATE USERS" << '\n';
}
}
Altough my query to create the users table is correct, and it does create the table it always returns 1. What's the reason? Did I do something wrong?
My Sqlite connector works just fine the first time I try to insert rows, but after it is closed and I run the program again it won't work at all.
Here is my constructor
Sqldatabase::Sqldatabase() {
open_connection("Database.db");
sqlite3_stmt *statement;
std::string sql = "SELECT id FROM articles ORDER BY id DESC LIMIT 1";
char *query = &sql[0];
if(sqlite3_prepare_v2(db, query, -1, &statement, 0) == SQLITE_OK && sqlite3_step(statement) == SQLITE_ROW) {
article_counter = sqlite3_column_int(statement, 0) + 1;
} else {
article_counter = 1;
}
}
Here is my preparedStatement method.
bool Sqldatabase::prepareStatement(std::string sql) {
char *query = &sql[0];
sqlite3_stmt *statement;
int result;
if (sqlite3_prepare_v2(db, query, sql.size(), &statement, 0) == SQLITE_OK) {
result = sqlite3_step(statement);
std::cout << sql << '\n';
sqlite3_finalize(statement);
if(result == SQLITE_DONE) {
return true;
}
}
std::cout << "SQL failed: " << sql << '\n';
return false;
}
And finally here is where I call the method.
bool Sqldatabase::create_ART(int ng_id, std::string title, std::string author, std::string text) {
//Creating article
std::ostringstream s;
s << "INSERT INTO articles (id, title, author, content, created) " <<
"VALUES (" << article_counter << ", '" << title << "', '" << author << "', '" << text << "' , CURRENT_DATE)";
std::string sql(s.str());
prepareStatement(sql);
//Adding article to newsgroup
std::ostringstream t;
t << "INSERT INTO contains VALUES ( " << article_counter << " , " << ng_id << ")";
std::string sql2(t.str());
article_counter++;
return prepareStatement(sql2);
}
My test script looks like this. And I already have a Newsgroup with id 1 in the database.
Sqldatabase db;
int main(int argc, char* argv[]){
std::cout << "-----Test of Memdatabase, Newsgroup and Article classes-----" << std::endl;
db = Sqldatabase();
db.create_ART(1, "Happy day", "John", "Sunday afternoon is pretty chill");
db.create_ART(1, "Chill day", "Peter", "Sunday afternoon is pretty chill");
}
Ah, you're trying to create a new record with the same id. ids are typically unique. try:
db.create_ART(2, "Chill day", "Peter", "Sunday afternoon is pretty chill");
I've got 2 or more databases ATTACHed to one SQLite database connection. Each database consists of 3 tables. To have better access for searching/filtering, I create a huge temporary table over all tables and databases like this:
"CREATE TEMPORARY TABLE temp_table AS "
"SELECT * FROM pb.name_table "
"LEFT JOIN pb.phone_table ON (pb.name_table.id=pb.phone_table.id) " \
"LEFT JOIN pb.email_table ON (pb.name_table.id=pb.email_table.id) " \
"UNION SELECT * FROM name_table " \<br>
"LEFT JOIN phone_table ON (name_table.id=phone_table.id) " \
"LEFT JOIN email_table ON (name_table.id=email_table.id);";
If something changes in a table, I have to recreate the temporary table. With an increasing amount of data, creating a temporary table takes some time, but since I'm having continuous read access to the table, my idea was as follows:
Create a thread, which creates a second temp table in background
Block access for the reading clients
DROP first temp table
Rename the second temp table
The problem is now: Creating a temporary table is a write access to the database, which blocks automatically all reading threads also.
Has anyone a good idea how I can handle this? I need read access while recreating the temporary table.
As long as all threads are part of the same program, you have control over all database connections.
So you can write the data in a completely separate database, and ATTACH is quickly later.
Thanks a lot for your answer. I changed my code and found out that I need a new database connection (sqlite3_open) in the working thread not to block the other thread. Also creating a TEMPORARY TABLE in the attached "temporary database" was not possible, because creating a temporary table doesn't allow a qualifier (like: x.temp_table), so I had to create a real table which consumes a lot of memory in our flash file system (which is not allowed).
But wait! I've got an idea
(2 hours later)
I did it! I open an empty database and attach alll relevant databases to the connection. I create a temporary table "in" the empty database which consumes no memory in flash, because it's temporary.
When I have to create a new table, I open another empty database and attach the relevant databases to the connection. When the operation is finished, I switch the old and the new connection. Code as follows:
#include <iostream>
#include "dbAccess.h"
#include <cstdio>
#include <string>
#include <cstring>
using namespace std;
bool inProgress = true;
DWORD WINAPI createTempTableThread(void *param);
int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
cout << "*";
return 0;
}
int main(void)
{
sqlite3* db = NULL;
HANDLE hThreadHandle = NULL;
CdbAccess *dba = new CdbAccess();
int i = 0;
db = dba->dbaConnect();
dba->dbaSetDatabase(db);
cout << "INFO: Creating initial temporary table. " << endl;
sqlite3_exec(dba->dbaGetDatabase(), "CREATE TEMPORARY TABLE temp_table AS " \
"SELECT * FROM pb.name_table " \
"LEFT JOIN pb.phone_table ON (pb.name_table.id=pb.phone_table.id) " \
"LEFT JOIN pb.email_table ON (pb.name_table.id=pb.email_table.id) " \
"UNION SELECT * FROM intern.name_table " \
"LEFT JOIN intern.phone_table ON (intern.name_table.id=intern.phone_table.id) " \
"LEFT JOIN intern.email_table ON (intern.name_table.id=email_intern.table.id);", NULL, NULL, NULL);
cout << "INFO: Creating initial temporary table finished. " << endl;
while(1)
{
hThreadHandle = CreateThread(0, 0, createTempTableThread, dba, 0, 0);
while(inProgress)
{
sqlite3_exec(dba->dbaGetDatabase(), "SELECT * FROM name_table WHERE id LIKE 1;", callback, NULL, NULL);
}
for(i = 0; i < 5; i++)
{
sqlite3_exec(dba->dbaGetDatabase(), "SELECT * FROM name_table WHERE id LIKE 2;", callback, NULL, NULL);
}
inProgress = true;
CloseHandle(hThreadHandle);
}
dba->dbaDisconnect();
return 0;
}
CdbAccess::CdbAccess()
{
hSemaphore = CreateSemaphore(NULL, 1, 1, 0);
}
CdbAccess::~CdbAccess()
{
}
sqlite3 *CdbAccess::dbaConnect()
{
sqlite3 *db;
static int num = 1;
int err = SQLITE_OK;
string attach = "ATTACH DATABASE \"";
string internal = "cbInternal.db";
if(num == 1)
{
cout << endl << "INFO: cbTemp1.db";
err = sqlite3_open("cbTemp1.db", &db);
num = 2;
}
else
{
cout << endl << "INFO: cbTemp2.db";
err = sqlite3_open("cbTemp2.db", &db);
num = 1;
}
if(err == SQLITE_OK)
{
cout << endl << "INFO: Temp database opened.";
err = sqlite3_exec(db, "ATTACH DATABASE \"cbInternal.db\" AS intern;", NULL, NULL, NULL);
if(err == SQLITE_OK)
{
cout << endl << "INFO: Internal database attached.";
err = sqlite3_exec(db, "ATTACH DATABASE \"0123456789.db\" AS pb;", NULL, NULL, NULL);
if(err == SQLITE_OK)
{
cout << endl << "INFO: Phone book attached.";
}
else
{
cout << endl << "ERROR: Attaching phone book: " << sqlite3_errmsg(db);
}
}
else
{
cout << endl << "ERROR: Attaching internal database: " << sqlite3_errmsg(db);
}
}
else
{
cout << endl << "ERROR: Opening database: " << sqlite3_errmsg(db);
}
return db;
}
int CdbAccess::dbaDisconnect(void)
{
int err = SQLITE_OK;
err = sqlite3_exec(db, "DETACH DATABASE pb;", NULL, NULL, NULL);
if(err == SQLITE_OK)
{
cout << endl << "INFO: Phone book detached.";
err = sqlite3_exec(db, "DETACH DATABASE intern;", NULL, NULL, NULL);
if(err == SQLITE_OK)
{
cout << endl << "INFO: Internal database detached.";
err = sqlite3_close(db);
if(err == SQLITE_OK)
{
cout << endl << "INFO: Database connection closed.";
}
else
{
cout << endl << "ERROR: Could not close database: " << sqlite3_errmsg(db);
}
}
else
{
cout << endl << "ERROR: Could not detach internal database: " << sqlite3_errmsg(db);
}
}
else
{
cout << endl << "ERROR: Could not detach phone book: " << sqlite3_errmsg(db);
}
return err;
}
sqlite3* CdbAccess::dbaGetDatabase(void)
{
return db;
}
void CdbAccess::dbaSetDatabase(sqlite3 * sqldb)
{
db = sqldb;
}
int CdbAccess::dbaGetTempTableAccess(void)
{
cout << endl << "INFO: Access requested.";
WaitForSingleObject(hSemaphore, INFINITE);
return 0;
}
int CdbAccess::dbaReleaseTempTableAccess(void)
{
cout << endl << "INFO: Access released.";
ReleaseSemaphore(hSemaphore, 1, NULL);
return 0;
}
DWORD WINAPI createTempTableThread(void *param)
{
int err = SQLITE_OK;
CdbAccess *d = (CdbAccess *)param;
sqlite3 *db;
cout << endl << "INFO: createTempTable: IN";
inProgress = true; // global variable for test porpose only
db = d->dbaConnect();
if(db != NULL)
{
cout << endl << "Thread: INFO: Creating temporary table. ";
err = sqlite3_exec(db, "CREATE TEMPORARY TABLE temp_table AS " \
"SELECT * FROM pb.name_table " \
"LEFT JOIN pb.phone_table ON (pb.name_table.id=pb.phone_table.id) " \
"LEFT JOIN pb.email_table ON (pb.name_table.id=pb.email_table.id) " \
"UNION SELECT * FROM intern.name_table " \
"LEFT JOIN intern.phone_table ON (intern.name_table.id=intern.phone_table.id) " \
"LEFT JOIN intern.email_table ON (intern.name_table.id=intern.email_table.id);", NULL, NULL, NULL);
}
if(err != SQLITE_OK)
{
cout << endl << "Thread: ERROR: Creating temporary table: " << sqlite3_errmsg(db);
}
else
{
cout << endl << "Thread: INFO: Creating temporary table finished. ";
}
d->dbaSetDatabase(db);
inProgress = false; // global variable for test porpose only
cout << endl << "Thread: INFO: createTempTable: OUT";
return 0;
}
Two tables (Teachers and Students) are created while the Id in Students is referenced to the TeacherId in Teachers using FOREIGN KEY. If we use two different methods to insert the values into Students:
1. sqlite3_exec();
2. sqlite3_bind();
The return message from sqlite3_errmsg() is not the same using these two methods:
1. sqlite3_exec(): return "foreign key constraints failed";
2. sqlite3_bind(): return "SQL logic error or missing database";
The message from sqlite3_errmsg() for sqlite3_exec() is more clearer than that for sqlite3_bind();
However, sqlite3_bind() is more convenient and efficient to insert values compared to sqlite3_exec();
My question: How to get a clearer returned error message for sqlite3_bind()?
The following is the full codes:
#include <string.h>
#include <stdio.h>
#include <iostream>
#include "sqlite3.h"
using namespace std;
sqlite3* db;
int first_row;
// callback function;
int select_callback(void *p_data, int num_fields, char **p_fields, char **p_col_names)
{
int i;
int* nof_records = (int*) p_data;
(*nof_records)++;
// first_row was defined in <select_stmt> function;
// if first_row == 1, print the first row
// and then set first_row = 0 to avoid the subsequent execution for the following rows.
if (first_row == 1)
{
first_row = 0;
for (i=0; i < num_fields; i++)
{ printf("%20s", p_col_names[i]);
}
printf("\n");
for (i=0; i< num_fields*20; i++)
{ printf("=");
}
printf("\n");
}
for(i=0; i < num_fields; i++)
{ if (p_fields[i])
{ printf("%20s", p_fields[i]);
}
else
{ printf("%20s", " ");
}
}
printf("\n");
return 0;
}
// With callback function;
void select_stmt(const char* stmt)
{ char *errmsg;
int ret;
int nrecs = 0;
first_row = 1;
ret = sqlite3_exec(db, stmt, select_callback, &nrecs, &errmsg);
if(ret!=SQLITE_OK)
{ printf("Error in select statement %s [%s].\n", stmt, errmsg);
}
else
{ printf("\n %d records returned.\n", nrecs);
}
}
// Without callback function;
void sql_stmt(const char* stmt)
{ char *errmsg;
int ret;
ret = sqlite3_exec(db, stmt, 0, 0, &errmsg);
if(ret != SQLITE_OK)
{ printf("Error in statement: %s [%s].\n", stmt, errmsg);
}
}
//////////////////////////////////////// Main /////////////////////////////////
int main()
{ cout << "sqlite3_open("", &db): " << sqlite3_open("./shcool.db", &db) << endl;
if(db == 0)
{ printf("\nCould not open database.");
return 1;
}
char *errmsg;
int result;
result = sqlite3_exec ( db,
"Drop TABLE IF EXISTS Teachers", // stmt
0,
0,
&errmsg
);
if ( result != SQLITE_OK )
{ cout << "\nCould not prepare statement: Drop TABLE: " << result << endl;
cout << "errmsg: " << errmsg << endl;
return 1;
}
result = sqlite3_exec ( db,
"Drop TABLE IF EXISTS Students", // stmt
0,
0,
&errmsg
);
if ( result != SQLITE_OK )
{ cout << "\nCould not prepare statement: Drop TABLE: " << result << endl;
cout << "errmsg: " << errmsg << endl;
return 1;
}
// CREATE TABLE Teachers;
sql_stmt("CREATE TABLE Teachers(Id integer PRIMARY KEY,Name text,Age integer NOT NULL)");
//////////////////////////// insert values into Teachers; /////////////////////////////////
sqlite3_stmt *stmt;
sqlite3_prepare(db, "PRAGMA foreign_keys = ON;", -1, &stmt, 0);
if ( sqlite3_prepare
( db,
"insert into Teachers values (:Id,:Name,:Age)", // stmt
-1, // If than zero, then stmt is read up to the first nul terminator
&stmt,
0 // Pointer to unused portion of stmt
)
!= SQLITE_OK )
{ printf("\nCould not prepare statement.");
return 1;
}
int index1, index2, index3;
index1 = sqlite3_bind_parameter_index(stmt, ":Id");
index2 = sqlite3_bind_parameter_index(stmt, ":Name");
index3 = sqlite3_bind_parameter_index(stmt, ":Age");
cout << index1 << endl;
cout << index2 << endl;
cout << index3 << endl;
printf("\nThe statement has %d wildcards\n", sqlite3_bind_parameter_count(stmt));
int id[] = {1, 2, 3};
string name[] = {"Zhang", "Hou", "Liu"};
int age[] = {28, 29, 31};
for ( int i = 0; i != 3; i++ )
{ if (sqlite3_bind_int
(stmt,
index1, // Index of wildcard
id[i]
)
!= SQLITE_OK)
{ printf("\nCould not bind sqlite3_bind_int.\n");
return 1;
}
if (sqlite3_bind_text
( stmt,
index2, // Index of wildcard
name[i].c_str(),
strlen(name[i].c_str()),
SQLITE_STATIC
)
!= SQLITE_OK)
{ printf("\nCould not bind sqlite3_bind_text.\n");
return 1;
}
if (sqlite3_bind_int
( stmt,
index3, // Index of wildcard
age[i]
)
!= SQLITE_OK)
{ printf("\nCould not bind sqlite3_bind_int.\n");
return 1;
}
// execute sqlite3_step(), and check the state of the statement
if (sqlite3_step(stmt) != SQLITE_DONE)
{ printf("\nCould not step (execute) stmt.\n");
return 1;
}
// reset the statement if you want to continue the sqlite3_bind().
cout << "sqlite3_reset(stmt): " << sqlite3_reset(stmt) << endl;
}
//////////////////////////// insert values into Students; /////////////////////////////////
// CREATE TABLE Students;
sql_stmt("CREATE TABLE Students (Id integer PRIMARY KEY, TeacherId integer, FOREIGN KEY(TeacherId) REFERENCES Teachers(id) )" );
//////// Method 1: use sqlite3_exec to insert values; ////////////
sql_stmt("INSERT INTO Students Values (0, 1)" );
sql_stmt("INSERT INTO Students Values (1, 2)" );
sql_stmt("INSERT INTO Students Values (2, 9)" );
cout << "sqlite3_errmsg: " << sqlite3_errmsg(db) << endl;
//////// Method 2: use sqlite3_bind to insert values; ////////////
result = sqlite3_exec ( db,
"Drop TABLE IF EXISTS Students", // stmt
0,
0,
&errmsg
);
if ( result != SQLITE_OK )
{ cout << "\nCould not prepare statement: Drop TABLE: " << result << endl;
cout << "errmsg: " << errmsg << endl;
return 1;
}
// CREATE TABLE Students;
sql_stmt("CREATE TABLE Students (Id integer PRIMARY KEY, TeacherId integer, FOREIGN KEY(TeacherId) REFERENCES Teachers(id) )" );
if ( sqlite3_prepare
( db,
"insert into Students values ( :Id,:TeacherId )", // stmt
-1, // If than zero, then stmt is read up to the first nul terminator
&stmt,
0 // Pointer to unused portion of stmt
)
!= SQLITE_OK )
{ printf("\nCould not prepare statement.");
return 1;
}
index1 = sqlite3_bind_parameter_index(stmt, ":Id");
index2 = sqlite3_bind_parameter_index(stmt, ":TeacherId");
cout << index1 << endl;
cout << index2 << endl;
printf("\nThe statement has %d wildcards\n", sqlite3_bind_parameter_count(stmt));
int studentId[] = {0, 1, 2};
/// if the FOREIGN KEY works, the teacherId should not be 9;
int teacherId[] = {1, 2, 9};
for ( int i = 0; i != 3; i++ )
{ if (sqlite3_bind_int
(stmt,
index1, // Index of wildcard
studentId[i]
)
!= SQLITE_OK)
{ printf("\nCould not bind sqlite3_bind_int.\n");
return 1;
}
if (sqlite3_bind_int
( stmt,
index2, // Index of wildcard
teacherId[i]
)
!= SQLITE_OK)
{ printf("\nCould not bind sqlite3_bind_int.\n");
cout << "sqlite3_errmsg: " << sqlite3_errmsg(db) << endl;
return 1;
}
// execute sqlite3_step(), and check the state of the statement
// cout << "sqlite3_errmsg: " << sqlite3_errmsg(db) << endl;
if ( result = sqlite3_step(stmt) != SQLITE_DONE )
{ printf("\nCould not step (execute) stmt.\n");
cout << "sqlite3_errmsg: " << sqlite3_errmsg(db) << endl;
cout << "result: " << result << endl;
return 1;
}
cout << "result: " << result << endl;
// reset the statement if you want to continue the sqlite3_bind().
cout << "sqlite3_reset(stmt): " << sqlite3_reset(stmt) << endl;
}
printf("\n");
// Print all;
select_stmt("select * from Teachers");
select_stmt("select * from Students");
sqlite3_close(db);
return 0;
}
It's recommended to use sqlite3_prepare_v2 instead of sqlite3_prepare. Excerpt:
The sqlite3_prepare_v2() and sqlite3_prepare16_v2() interfaces are recommended for all new programs. The two older interfaces are retained for backwards compatibility, but their use is discouraged. In the "v2" interfaces, the prepared statement that is returned (the sqlite3_stmt object) contains a copy of the original SQL text. This causes the sqlite3_step() interface to behave differently in three ways:
[Point 1 omitted]
2. When an error occurs, sqlite3_step() will return one of the detailed error codes or extended error codes. The legacy behavior was that sqlite3_step() would only return a generic SQLITE_ERROR result code and the application would have to make a second call to sqlite3_reset() in order to find the underlying cause of the problem. With the "v2" prepare interfaces, the underlying reason for the error is returned immediately.
[Point 3 omitted]