Simple use of Fmdb

Fmdb Common classes:

Fmdatabase: A single SQLite database for executing SQL statements.
Fmresultset: Executes a query with a fmdatabase result set, which is similar to the cursor on Android.
Fmdatabasequeue: This class is used when multiple threads are executing queries and updates.

To create a database:

db = [Fmdatabase Databasewithpath:database_path];

1, when the database file does not exist, Fmdb will create a.

2, if you pass in a parameter is empty string: @ "", then Fmdb will create the database in the temporary file directory, the database is disconnected, the database file is deleted.

3. If you pass in a parameter that is NULL, it will establish a database in memory and the database file is deleted when the database is disconnected.

Open the database:

[DB Open]

Returns the bool type.

To close the database:

[DB Close]

To create a table:

if ([DB Open])

{

NSString *sqlcreatetable = [NSString stringwithformat:@"CREATE TABLE IF not EXISTS '%@ ' ('%@ ' INTEGER PRIMARY KEY A  　　Utoincrement, '%@ ' text, '%@ ' INTEGER, '%@ ' text) ', tablename,id,name,age,address];   BOOL res = [db executeupdate:sqlcreatetable];

　　if (!res) {

　　　　　　NSLog (@"error when creating DB table");

} Else {

　　　　　　　NSLog (@"success to creating DB table");

}

[DB close];

}

Add Data:

if ([db Open]) {

NSString *insertsql1= [NSString stringWithFormat:

@"INSERT into '%@ ' ('%@ ', '%@ ', '%@ ') VALUES ('%@ ', '%@ ', '%@ ')",

TABLENAME, NAME, age, ADDRESS, @"Zhang San", @ "@", @"Jinan"];

BOOL res = [db EXECUTEUPDATE:INSERTSQL1];

　　if (!res) {

NSLog (@"error when insert DB table");

} Else {

NSLog (@"success to insert DB table");

}

[DB close];

}

To modify the data:

if ([db Open]) {

NSString *updatesql = [NSString stringWithFormat:

@"UPDATE '%@ ' SET '%@ ' = '%@ ' WHERE '%@ ' = '%@ '",

TABLENAME, age, @ "All", age, @"13"];

BOOL res = [db executeupdate:updatesql];

　if (!res) {

NSLog (@"error when update db table");

} Else {

NSLog (@"Success to update DB table");

}

[DB close];

}

Delete data:

if ([db Open]) {

NSString *deletesql = [NSString stringWithFormat:

@"Delete from%@ where%@ = '%@ '",

TABLENAME, NAME, @"Zhang San"];

BOOL res = [db executeupdate:deletesql];

if (!res) {

NSLog (@"error when delete db table");

} Else {

NSLog (@"success to delete db table");

}

[DB close];

}

Database Query Operations:

The query operation uses ExecuteQuery and involves Fmresultset.

if ([db Open]) {

NSString * sql = [NSString stringWithFormat:

@"SELECT * from%@", TABLENAME];

Fmresultset * rs = [db Executequery:sql];

while ([Rs next]) {

　　　　int Id = [Rs intforcolumn:id];

NSString * name = [Rs Stringforcolumn:name];

NSString * age = [Rs stringforcolumn:age];

NSString * address = [Rs stringforcolumn:address];

NSLog (@"id =%d, name =%@, age =%@ address =%@", ID, name, age, address);

}

[DB close];

}

Fmdb's Fmresultset provides several ways to get different types of data:

Multi-threaded database operations:

If you use a multi-threaded database in your application, you need to use Fmdatabasequeue to ensure thread safety. It is not common in the application to use a Fmdatabase object in multiple threads to manipulate the database, which can cause confusion in database data. For multi-threaded operation of database security, Fmdb uses Fmdatabasequeue, using Fmdatabasequeue is very simple, first with a database file address to the initial fmdatabasequeue, and then you can be a closure (block) Passed into the Indatabase method. Operate the database in a closure without directly participating in the management of the fmdatabase.

Fmdatabasequeue * queue = [Fmdatabasequeue Databasequeuewithpath:database_path];

dispatch_queue_t q1 = dispatch_queue_create ("queue1", NULL);

dispatch_queue_t q2 = dispatch_queue_create ("Queue2", NULL);

Dispatch_async (Q1, ^{

for (int i = 0; i < ++i) {

[Queue indatabase:^ (Fmdatabase *db2) {

NSString *insertsql1= [NSString stringWithFormat:

@"INSERT into '%@ ' ('%@ ', '%@ ', '%@ ') VALUES (?,?,?)",

TABLENAME, NAME, age, ADDRESS];

NSString * name = [NSString stringwithformat:@"Jack%d", I];

NSString * age = [NSString stringwithformat:@"%d", 10+i];

　　　　　BOOL res = [DB2 EXECUTEUPDATE:INSERTSQL1, Name, age,@"Jinan"];

I F (!res) {

NSLog (@"error to Inster data:%@", name);

} Else {

NSLog (@"succ to Inster Data:%@", name);

}

}];

}

});

Simple use of Fmdb