My iPhone application has a code like this to delete a table and re-create it.
const char *sql = [#"DROP TABLE mytable" cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *statement;
if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL) == SQLITE_OK) {
sqlite3_step(statement);
NSLog(#"dropped.");
} else {
NSLog(#"error. %s", sqlite3_errmsg(database));
}
sqlite3_finalize(statement);
// ...
// DO SQL LIKE `CREATE TABLE mytable` here.
In most cases, this code works.
But error reports say, the table still exist after the first SQL (DROP TABLE mutable) ran without an error in some rare cases. And I have never experienced that case on my devices.
Has anyone experienced this? or any information?
Related
I have 12 columns in my table. In which last two columns are added newly. I use sqlite3 database. Database is created and query is executed correctly if I use where clause for any other columns other than lastly created two new columns. The last two columns return NULL string which makes the app crash throwing Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: ' *+[NSString stringWithUTF8String:]: NULL cString'**
When the query is executed in SQL Manager I could retrieve last two columns. I suppose somewhere something is wrong in my prepare statement.
NSString *query = #"select * from tableName where lastColumn = 'Value'";
const char *sqlStatement = [query UTF8String];
sqlite3_stmt *compiledStatement;
NSLog(#"could not prepare statement: %s\n", sqlite3_errmsg(database));
if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {
// Loop through the results and add them to the feeds array
while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
}
Please Help me on this. I totally have no clue where the last two columns have gone.. :)
You're passing NULL to stringWithUTF8String: method, which is not allowed. You should check the value you get from sqlite before instantiating NSString object.
const char *ctext = sqlite3_column_text(compiledStatement, 2);
if (ctext) {
text = [NSString stringWithUTF8String:ctext];
}
When you added new columns, values for this columns in all existing rows were set to NULL.
I am experiencing issues with deleting a row / data record from an SQLite database located on the iPhone. I followed advice given in the following post, but the result code from SQLite is 5. From the SQLite reference manual, 5 means:
SQLITE_BUSY 5 /* The database file is locked */
Has anyone else come across this problem or have any ideas why this would be the case?
Here is an excerpt of my code (dbrc is set to 5):
NSString *retrievedContactID = [archivedContact objectForKey:#"contact_id"];
sqlite3 *database = [FollowUPAppDelegate checkAndCreateDatabase];
NSString *deleteSQL = [NSString stringWithFormat:#"DELETE FROM Contacts WHERE contact_id = %#", retrievedContactID];
const char *delete_stmt = [deleteSQL UTF8String];
sqlite3_stmt *compiledStatement;
int dbrc; //database return code
dbrc = sqlite3_prepare_v2(database, delete_stmt, -1, &compiledStatement, NULL);
dbrc = sqlite3_step(compiledStatement);
sqlite3_finalize(compiledStatement);
compiledStatement = NULL;
if (dbrc != 101) { //anything except 101 (SQLITE_DONE for delete, *not* SQLITE_OK)
NSLog(#"Error deleting contact from database: result code %i", dbrc);
return;
}
else {
NSLog(#"deleted the customer from datasets");
}
sqlite3_close(database);
This means. your database is being used by some other process. you have to stop the other process and proceed.
I can give you an example. when you are accessing a database from your app and if you try to change the content using some external sqlite manager you would get this busy error. The solution to this problem is,stop your app and try.
You problem is similar. Your database is locked by some other process.
I am using this code to insert the data in my database
but it is not working..
My data is not being inserted in the table ..
what can be the problem??
in function.h
+(BOOL)insertStudentinfoData:(NSString *)first_name last_name:(NSString *)last_name phone_num:(NSString *)phone_num;
in function.m
+(BOOL)insertStudentinfoData:(NSString *)first_name last_name:(NSString *)last_name phone_num:(NSString *)phone_num
{
NSString *sql = [NSString stringWithFormat:#"insert into add_data
values(NULL,'%#','%#','%#')",first_name,last_name,phone_num];
return [DBOperation executeSQL:sql];
}
And I am giving the data from this
[Function insertStudentinfoData:#"hello" last_name:#"w3qrq" phone_num:#"efew"];
but my data is not being inserted in the table
////In DBOperation.h
+(BOOL) executeSQL:(NSString *)sqlTmp {
if(conn == SQLITE_OK) {
NSLog(#"\n\n%#",sqlTmp);
const char *sqlStmt = [sqlTmp cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *cmp_sqlStmt1;
int returnValue = sqlite3_prepare_v2(database, sqlStmt, -1, &cmp_sqlStmt1, NULL);
returnValue == SQLITE_OK ? NSLog(#"\n Inserted \n") :NSLog(#"\n Not Inserted \n");
sqlite3_step(cmp_sqlStmt1);
sqlite3_finalize(cmp_sqlStmt1);
if (returnValue == SQLITE_OK) {
return TRUE;
}
}
return FALSE;
}
I guess you are passing the NULL value for PRIMARY KEY, first reset the simulator
if you are not specifying the column name and inserting the values then you should pass the value for each column in particular order of column created otherwise its a good idea to specify column
NSString *sql = [NSString stringWithFormat:#"INSERT INTO add_data
(first_name,last_name,phone_num) VALUE('%#','%#','%#')",first_name,last_name,phone_num];
or
NSString *sql =[NSString stringWithFormat:#"INSERT INTO add_data
(first_name,last_name,phone_num,email,address,city,zip) VALUES
('%#','%#','%#','%#','%#','%#','%#');",first_name,last_name,phone_num,email,address,city,zip];
are you sure that the database is initialized correctly? I always had trouble with the DB not actually there. Which DB Framework are you using?
[EDIT] do you see this log statement?
NSLog(#"\n\n%#",sqlTmp);
Did you write the DBOperations class yourself? I think there is some issue there with the static variable you're using. I'd suggest to either use an existing db framework like fmdb or something, or else modify your class so that it uses the Singleton Pattern.
Oh, and one thing: Are you calling all methods from the same thread? SQlite DBs are not thread safe!
[edit2] You can use the link provided here: SQLite3 error - iOS to check what the value in returnValue actually states - and then figure out the underlying error.
It's probably best for now to modify your not inserted statement like this:
returnValue == SQLITE_OK ? NSLog(#"\n Inserted \n") :NSLog(#"\n Not Inserted with code: %i\n",returnValue);
What if you provide the names of the columns to be inserted:
insert into T (foo, bar, baz)
values( ....)
Try it this way to see full error code and message:
The sql comes as NSString *, do not convert it into a cstring.
int rc;
sqlite3_stmt *sel;
if ((rc = sqlite3_prepare_v2(db_handle, [sql UTF8String], -1, &sel, NULL)) != SQLITE_OK) {
NSLog(#"cannot prepare '%#': %d (%s)", sql, rc, sqlite3_errmsg(db_handle));
return;
}
if (sqlite3_step(sel) != SQLITE_DONE) {
NSLog(#"error insert/update: '%s'", sqlite3_errmsg(db_handle));
...
This is the code I'm using to select some records from my database. I'm binding two dates into my sql, however, when I get to sqlite3_step I get SQLITE_DONE where I should be getting SQLITE_ROW. It looks like its processing the bindings rather than querying the data.
What am I doing wrong ?
NSString *startDateRangeString = #"2000-05-01";
NSString *endDateRangeString = #"2011-05-01";
sqlite3 *database;
int result = sqlite3_open("mydb.db", &database);
if(result != SQLITE_OK)
{
NSLog(#"Could not open db.");
}
const char *sql = "select pid from tmp where due >= '%#' and due < '%#' order by due, pid;";
sqlite3_stmt *statementTMP;
int error_code = sqlite3_prepare_v2(database, sql, -1, &statementTMP, NULL);
if(error_code == SQLITE_OK) {
sqlite3_bind_text(statementTMP, 1, [startDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(statementTMP, 2, [endDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
int step_error_code = sqlite3_step(statementTMP);
while(sqlite3_step(statementTMP) == SQLITE_ROW) // I get 101 aka SQLITE_DONE
{
NSLog(#"Found!!");
}
}
sqlite3_finalize(statementTMP);
sqlite3_close(database);
I think your SQL is bad. Instead of %# you should use ? for the positional parameters.
I strongly suggest using a wrapper to simplify life. FMDB is a great one at http://github.com/ccgus/fmdb.
char *statementTMP = "select pid from tmp where due >= '?1' and due < '?2' order by due, pid";
....
sqlite3_bind_text(statementTMP, 1, [startDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(statementTMP, 2, [endDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
This is by design.
sqlite3_step returns SQLITE_ROW for each row in the resultset, and SQLITE_DONE to indicate there are no more rows. So if a resultset contains N rows, then N calls would return SQLITE_ROW and (N+1)st returns SQLITE_DONE. An empty resultset is not in any way special, it follows the same logic with N=0 (so the very first call returns SQLITE_DONE). This allows client code to handle all resultsets uniformly.
Hope that helps.
Let me know if you need anymore help.
PK
If I read correctly.. You are not executing the statement.. you are just preparing.. you have to do both..
this part just prepare the query
if (sqlite3_prepare_v2(database, sql, -1, &stmt, NULL) != SQLITE_OK)
{
NSLog(#"SQL Warning: failed to prepare statement
with message '%s'.", sqlite3_errmsg(database));
}
This part actually executes the query
if(sqlite3_exec(database, sql, nil, &stmt, &errmsg) == SQLITE_OK)
{
NSLog(#"it means that you query executed correctly");
if(sqlite3_step(stmt) == SQLITE_ROW)
{
NSLog(#"Found!!");
}
}else
{
NSLog(#"SQL Warning: '%s'.", sqlite3_errmsg(database));
}
=)
I have a sqlite database and I am adding to it new words. The problem is that I can see them added to a table only after restarting application. The "SELECT" statement doesn't "see" newly added elements before restarting application.
Why may this happen?
I am creating some kind of a dictionary. Here is how I add new items:
const char *sql_query = "INSERT INTO words(word) VALUES(?)";
if(sqlite3_prepare_v2(database, sql_query, -1, &addWordsStmt, NULL) != SQLITE_OK)
{
return FALSE;
}
sqlite3_bind_text(addWordsStmt, 1, [ word UTF8String], -1, SQLITE_TRANSIENT);
if( sqlite3_step(addWordsStmt) != SQLITE_DONE)
NSAssert1(0, #"Error while inserting data. '%s'", sqlite3_errmsg(database));
sqlite3_reset(addWordsStmt);
sqlite3_finalize(addWordsStmt);
And here is my retrieval code:
const char *sql_query = "SELECT word FROM words WHERE id=?";
if(sqlite3_prepare_v2(database, sql_query, -1, &getWordsStmt, NULL) != SQLITE_OK)
{
return;
}
sqlite3_bind_int(getWordsStmt, 1, wordid);
if( sqlite3_step(getWordsStmt) != SQLITE_ROW)
{
NSLog(#"Error while getting data. '%s'", sqlite3_errmsg(database));
sqlite3_reset(getWordsStmt);
return;
}
NSString *word = [NSString stringWithUTF8String:(char *)sqlite3_column_text(getWordsStmt, 0)];
sqlite3_reset(getWordsStmt);
sqlite3_finalize(getWordsStmt);
My guess is that you are in a transaction. There must be some other calls during your open and close routines that are wrapping your calls in a transaction and not displayed in your code fragments.
That is why you don't see the new words until you application exits
There's your problem:
const char *sql_query = "SELECT word FROM words WHERE id=?";
This isn't how you use SQL. Instead, you should be using SELECT word FROM words; and stepping to get each row as long as you're getting SQLITE_ROW until you get SQLITE_DONE. That will get you all your words. How are you going to find a word by id when you don't know the id of newly added words?