i have created sqlite database as follow
NSString * sqlStmt =#"CREATE TABLE IF NOT EXISTS SONGS (ID INTEGER PRIMARY KEY AUTOINCREMENT, MOVIENAME TEXT, SONGNAME TEXT)";
after deleting row 7 in database the id values are 1,2,3,4,5,6,8,9... by using following code where idNumber =7.
const char *dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath, &_SQliteDB) == SQLITE_OK)
{
NSString *sql = [NSString stringWithFormat:#"delete from SONGS where ID=%d",idNumber];
const char *del_stmt = [sql UTF8String];
char *error ;
if (sqlite3_exec(_SQliteDB,del_stmt, NULL, NULL, &error) == SQLITE_OK)
{
NSLog(#"sucessfully delete");
} else
{
NSLog(#"unable to delete");
}
sqlite3_close(_SQliteDB);
}
else
{
NSLog(#"unable to open");
}
i need to rearrange that order as sequentially as 1,2,3,4,5,6,7,8?
Any help would be appreciated.
You shouldn't re-order IDs, because other tables may have reference for this ID. Because if any how you are able to do that then next problem will arise in front of you.
For example:- You have rows 1, 2, 3 and you delete 2, then you have 1, 3. And you sorted this any how. Now Issue is when you going to add new item it starts with 4 not 3.
In your case, I recommend using the Row_Number if it's for a display reason.
There's no problem having gaps in a database.
If you want the order as sequentially, ORDER BY is what you are looking for.
After deleting, retrieve records using select query as shown below :
NSString *select = #"SELECT * FROM SONGS ORDER BY ID"
For more detail about ORDER BY , refer to link1 and for how to use it in iOS, refer to link2
You must define all data from database to new array or list.After that you must delete table and rewrite all data from array or list to database.
You can look for android studio solution ;
https://stackoverflow.com/a/57862686/8363647
Related
Is it possible to execute two or more select statement in one query in SQLite? For example,
We can execute create or insert query,
NSString *create_query = #"create table if not exists Employee (id integer primary key, firstName text, lastName text);create table if not exists Department (id integer primary key, department text, devision text)";
By using,
sqlite3_exec(self.contactDB,[create_query UTF8String], NULL, NULL, &errorMessage) == SQLITE_OK)
we can execute it.
But if query is something like,
NSString *select_query = #"select * from Employee;select * from Department";
Then is it possible to execute? If yes then how to differentiate data from sqlite3_step?
Generally we are fetching data like,
if (sqlite3_prepare_v2(self.contactDB, [select_query UTF8String], -1, &statement, NULL) == SQLITE_OK) {
NSLog(#"prepared from data get");
while (sqlite3_step(statement) == SQLITE_ROW) {
NSString *department = [[NSString alloc]initWithUTF8String:(const char*)sqlite3_column_text(statement, 1)];
NSString *devision = [[NSString alloc]initWithUTF8String:(const char *)sqlite3_column_text(statement, 2)];
NSLog(#"Department : %#, Devision : %#",department,devision);
}
NSLog(#"errror1 is %s",sqlite3_errmsg(self.contactDB));
}
But if there is a two select statement then how to identify column and row in sqlite3_step?
We can execute two select statements together (i.e. select * from Employee;select * from Department ) in terminal, so it should some way in iOS I think.
Yes, you can use sqlite3_exec() to execute two SELECT statements in one call. You just have to provide a callback function where you handle the result rows. I've never used that feature, and how I understand the doc you're on your own to distinguish the rows of each statement; perhaps one can use the column count for that.
I advise against using sqlite3_exec() that way; it seems rather tedious and error-prone. sqlite3_prepare_*() should be the way to go, and it can only handle one result set (SELECT query), but you can have open multiple statements at a time, represented by the ppStmt handle. If you have problems with that you should describe them instead of posting a XY Problem question.
We can perform this by using C style callback function with sqlite3_exec.
There is no proper code available on internet (I haven't found!) so i would like to answer with code sample.
We can implement C - style callback method like
int myCallback(void *parameter, int numberOfColumn, char **resultArr, char **column)
{
NSLog(#"number of column %d",numberOfColumn); // numberOfColumn is return total number of column for correspond table
NSString *columnName = [[NSString alloc]initWithUTF8String:column[0]]; // This will return column name column[0] is for first, column[1] for second column etc
NSLog(#"column name is %#",columnName);
NSString *result = [[NSString alloc]initWithUTF8String:resultArr[2]]; // resultArr returns value for row with respactive column for correspond table. resultArr[2] considered as third column.
NSLog(#"result is %#",result);
return 0;
}
And we can call this callback function in our sqlite3_exec function like,
NSString *getData = #"select * from Department;select * from Employee";
if (sqlite3_exec(self.contactDB, [getData UTF8String], myCallback, (__bridge void *)(self), &err) == SQLITE_OK ) {
if (err) {
NSLog(#"error : %s",err);
}
else {
NSLog(#"executed sucessfully");
}
}
We have make bride : (__bridge void *)(self) as parameter of sqlite3_exec. We can pass NULL in this case because we have implemented c style function. But if we implement Objective - c style function or method then we must pass (__bridge void *)(self) as parameter.
So, By callback function we can execute multiple queries in one statement whether it is select type queries or else.
Reference : One-Step Query Execution Interface
I am trying to insert values into new table added, my development app works fine whereas, my testing app its giving error SQLITE MISUSE when inserting data to new table, when i check the sqlite file it contains that table, but if i have app without login then try to login again, it works fine, i am not understanding why SQLITE MISUSE error, in this case update will not work.
Add Table :
createSQL = [NSString stringWithFormat:#"CREATE TABLE if not exists [%#] (id integer PRIMARY KEY AUTOINCREMENT, title text, description text, favourite text, template text, modified_date text)", NEW_TABLE];
if (sqlite3_exec (database, [createSQL UTF8String],NULL, NULL, &errorMsg) != SQLITE_OK)
{
sqlite3_close(database);
NSLog(#"Error in creating Inbox table: %s",errorMsg);
}
Insert :
sqlite3_stmt *stmt;
int sqlError;
NSString *query = [NSString stringWithFormat:#"INSERT INTO %# (title, description, favourite, template, modified_date) values (?,?,?,?,?)", NEW_TABLE];
const char *zSql = [query UTF8String];
sqlError = sqlite3_prepare_v2(database, zSql, -1, &stmt, nil);
if (sqlError == SQLITE_OK) {
// insert data
} else {
DLog(#"Error - %d while preparing startement - %#", sqlError, query);
}
I have a area table in sqlite database. Everytime i am just performing insert operation onto the sqlite database. How can i check if any record exists or not. If not exist simply insert. If exist then update records.
Please help me.
you can do easily "insert or ignore into tbl_name"
here you can see the example
http://www.raywenderlich.com/913/sqlite-tutorial-for-ios-making-our-app
this would be usefull for you....
http://www.sqlite.org/lang_conflict.html
Yes, you can do that with a single query.
INSERT ON CONFLICT IGNORE should help you: http://www.sqlite.org/lang_conflict.html
Put a unique key on the name, this will create a conflict when you try inserting a record if the name already exists.
The default is ABORT, so without the IGNORE, the statement will return an error. If you don't want that, use IGNORE.
You can do INSERT OR REPLACE if you have a primary key on the table. For example:
sqlite3 *database = NULL;
NSString *documentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSString *path = [documentsPath stringByAppendingPathComponent:#"test.sqlite"];
int rc = sqlite3_open([path UTF8String], &database);
NSAssert(rc == SQLITE_OK, #"Open failed");
// note, use PRIMARY KEY when creating table
rc = sqlite3_exec(database, "CREATE TABLE IF NOT EXISTS test (animal TEXT PRIMARY KEY, sound TEXT)", NULL, NULL, NULL);
NSAssert(rc == SQLITE_OK, #"Create failed: %s", sqlite3_errmsg(database));
// create a record that will be replaced by the subsequent `INSERT OR REPLACE`
rc = sqlite3_exec(database, "INSERT INTO test (animal, sound) VALUES ('dog', 'meow')", NULL, NULL, NULL);
NSAssert(rc == SQLITE_OK, #"INSERT failed: %s", sqlite3_errmsg(database));
// this will REPLACE entry if value with same PK found, otherwise it would INSERT
rc = sqlite3_exec(database, "INSERT OR REPLACE INTO test (animal, sound) VALUES ('dog', 'woof')", NULL, NULL, NULL);
NSAssert(rc == SQLITE_OK, #"INSERT failed: %s", sqlite3_errmsg(database));
// now retrieve values and make sure it worked like we thought it would
sqlite3_stmt *statement = NULL;
rc = sqlite3_prepare_v2(database, "SELECT animal, sound FROM test", -1, &statement, NULL);
NSAssert(rc == SQLITE_OK, #"prepare SELECT failed: %s", sqlite3_errmsg(database));
while ((rc = sqlite3_step(statement)) == SQLITE_ROW) {
const unsigned char *animal = sqlite3_column_text(statement, 0);
const unsigned char *sound = sqlite3_column_text(statement, 1);
NSLog(#"%s goes %s", animal, sound);
}
NSAssert(rc == SQLITE_DONE, #"step failed: %s", sqlite3_errmsg(database));
sqlite3_finalize(statement);
sqlite3_close(database);
And that will report that the INSERT OR REPLACE replaced the previous value rather than inserting second record:
2013-11-21 08:59:25.285 AnimalSounds[53549:70b] dog goes woof
If you don't have primary key, rather than this simple INSERT OR REPLACE, you'd have to break it into two steps, either:
Look for record with SELECT: If found, do UPDATE; if not found, do INSERT.
First DELETE any records that would match whatever criteria you want, and then do INSERT.
This first approach is a bit safer, but you could use the second approach if you had to (though you would probably use transactions a do a ROLLBACK if you had any problems). Needless to say, the INSERT OR REPLACE approach is even easier, but requires a primary key.
First call get record query in Database. Here I am add a example, I am checking that user login information available in database or not. So add below code. IF User record is available than i get record array otherwise nil.
+(NSArray*)getTBL_LOGIN
{
NSMutableArray *Favourite=[[NSMutableArray alloc]init];
sqlite3 *database;
TabBarAppDelegate *x=(TabBarAppDelegate*)[[UIApplication sharedApplication]delegate];
if(sqlite3_open([[x dataBasePath] UTF8String],&database) == SQLITE_OK) {
NSString *str = [NSString stringWithFormat:#"select * from tbl_login"];
const char *sqlStmt=[str UTF8String];
sqlite3_stmt *compiledStmt;
if(sqlite3_prepare_v2(database, sqlStmt, -1, &compiledStmt, NULL) == SQLITE_OK) {
while(sqlite3_step(compiledStmt)==SQLITE_ROW)
{
NSString *uid=[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStmt, 0)];
NSString *username=[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStmt, 1)];
NSDictionary *d=[NSDictionary dictionaryWithObjectsAndKeys:uid,#"uid",username,#"username",nil];
[Favourite addObject:d];
}
}
sqlite3_finalize(compiledStmt);
}
sqlite3_close(database);
if([Favourite count]>0)
{
NSArray *ar=[NSArray arrayWithArray:Favourite];
return ar;
} else {
return nil;
}
}
If you get the record count >=1 then record exist so you have to call update query if you get record count 0 than record is not available in database so you have to call insert query
In a situation where I imported all updates into another database table, I could use following:
-- Existing table: t(uc UNIQUE, v1, v2, v3);
-- Updates table: ut(uc UNIQUE, v2);
INSERT OR REPLACE INTO t
SELECT ut.uc, et.v1, ut.v2, et.v3 FROM ut
LEFT JOIN t AS et ON ut.uc=et.uc;
This statement will insert new rows from ut into t. Existing rows are replaced with a row containing new data from ut and existing data from t.
For this to work, you must have a UNIQUE column (which makes sense as you are looking for a row update or insert a new one), and have new data available so it can be queried (in same or another database).
This worked for me, hope it may help you.
Another solution, maybe with better performance is using two statements:
UPDATE t SET v1='some value', v2=123 WHERE unique_col='some_id';
INSERT OR IGNORE t(v1, v2, unique_col) VALUES('some value', 123, 'some_id');
UPDATE will become a null operation when 'some_id' is not found.
INSERT will ignore all existent 'some_id'.
I'm developing for iOS and I have a previous database really poorly constructed. Now there is already 140 sealed but in my update I make a new database but I can not delete the data... How can I change the data from database A to database B ? I use sqlite3 in xCode 5
Here is an example code altering a column in a database table:
- (void)alterDB {
sqlite3_stmt *statement;
sqlite3_stmt *selectStmt;
const char *columnExists = "select callCount from lastCall";
//Alter the table ONLY IF column we want doesn't exist
if (sqlite3_prepare_v2(database, columnExists, -1, &selectStmt, NULL) != SQLITE_OK)
{
NSString *updateSQL = [NSString stringWithFormat:#"ALTER TABLE lastCall ADD COLUMN callCount INTEGER"];
const char *update_stmt = [updateSQL UTF8String];
sqlite3_prepare_v2(database, update_stmt, -1, &statement, NULL);
if (sqlite3_step(statement) == SQLITE_DONE) {
NSLog(#"DATABASE ALTERED");
} else {
NSLog(#"error altering database");
}
}
}
I hope this gives you an idea.
Write migration code,
that will select the data from Database A and will insert it into Database B.
When dealing with different schemas, I have a method that I always call when opening the database that checks the schema version in a table set aside for that purpose and then doing any alterations as needed to the schema.
- (void) checkSchema {
if([[self preferenceForKey:#"SchemaVersion"] isEqualToString: #"1"]) {
[db sqlExecute:#"create table Documents(documentID int, description text, type text, url text, modifiedDate text, read int, fileName text, needsUpdate int, primary key(documentID,type));"];
[self setPreference:#"2" ForKey:#"SchemaVersion"];
}
// etc.
}
So while developing, I can add schema changes and no matter what version of the app someone is using, when they upgrade they will get the latest schema changes.
It is because of this, and the work of changing all my accessor methods to the database that I am now using SimpleDB (https://github.com/AaronBratcher/SimpleDB), a key/value db I wrote. Completely different way of accessing data that makes things a lot simpler.
I'm a noob when it comes to sqlite and not quite sure how to do this.
I want a database with a bunch of row, containing one word each. When the user types a word, I will validate it by checking if its in the database.
Things I dont have, I guess, and don't know how to create, is an index? How do I insert that? How do I write the query to take advantage of index?
I also have two columns in there, "id and word". Is it good to have the id or does it just take up space?
This is what I got so far:
CREATE TABLE words (id INTEGER PRIMARY KEY, word VARCHAR(15));
I don't want words longer then 15 characters, so I set the VARCHAR(15);
INSERT INTO words(word) VALUES('hello');
INSERT INTO words(word) VALUES('bye');
etc. for all words
And to check a word:
NSString *sql = [NSString stringWithFormat:#"SELECT EXISTS(SELECT 1 FROM words WHERE word=\"%#\" LIMIT 1)", word];
const char *sqlStatement = [sql UTF8String];
if (sqlite3_prepare_v2(db, sqlStatement, -1, &selectStmt, NULL) == SQLITE_OK)
{
int count = 0;
while(sqlite3_step(selectStmt) == SQLITE_ROW)
{
count = sqlite3_column_int(selectStmt, 0);
}
NSLog(#"COUNT: %i",count);
//If count is 1, we have a match.
}
Yes. Your Statement is ok.
You can also use ' intead of ":
NSString *sql = [NSString stringWithFormat:#"SELECT EXISTS(SELECT 1 FROM words WHERE word='%#' LIMIT 1)", word];
Is it good to have the id or does it just take up space?
It depends on your need, I will suggest you should keep an Id field as primary key.
For creating index you can use:
CREATE INDEX yourIndexName ON yourTableName ( yourColumnName )
For more about indexing check sqlite