IOS Data Storage FMDB

Fmdb has three main classes
1. Fmdatabase
A Fmdatabase object represents a separate Sqllite database
Used to execute SQL statements

2.FMResultSet
Result collection after query execution using fmdatabase

3.FMDatabaseQueue
Used to execute multiple queries or updates in multiple threads, which is thread-safe

There are three types of file paths
1. Specific file path
Automatically created if it does not exist

2. Empty string @ ""
An empty database is created in the temp directory
The database file is also deleted when the Fmdatabase connection is closed

3.nil
An in-memory staging database is created and the database is destroyed when the Fmdatabase connection is closed

Creating databases and Tables

#import "ViewController.h" @interface Viewcontroller () @property (nonatomic,strong) fmdatabase * db;-(ibaction) InsertData: (ID) sender;-(ibaction) Updata: (ID) sender;-(ibaction) DeleteData: (ID) sender;-(ibaction) Qurey: (ID)        sender; @end @implementation viewcontroller-(void) viewdidload {[Super viewdidload]; Gets the path of the sandbox NSString * Filename=[nssearchpathfordirectoriesindomains (nsdocumentdirectory, Nsuserdomainmask, YES).        Lastobject stringbyappendingpathcomponent:@ "Student.db"];        1. Create a DB instance Object self.db =[fmdatabase Databasewithpath:filename];        2. Open the database if ([self.db Open]) {NSLog (@ "Database open successfully!"); Create database table BOOL result= [self.db executeupdate:@ "CREATE table if not exists t_student (ID integer PRIMARY key autoincre        ment, name Text,age integer) "]; if (result) {NSLog (@ "CREATE TABLE succeeded!");} else{NSLog (@ "Failed to create TABLE!");}} else{NSLog (@ "Database open failed!");}}

Inserting data

Insert Data-(ibaction) InsertData: (ID) Sender {        BOOL result=[self.db executeupdate:@ "INSERT into t_student (ID, name,age ) VALUES (?,?,?) ", @3,@" Hu Xing ", @38];        if (result) {                NSLog (@ "Insert data successfully!");    } else{                NSLog (@ "Insert number failed!");    }    }

modifying data

Modify Data-(ibaction) Updata: (ID) Sender {        BOOL result =[self.db executeupdate:@ "update t_student Set id =?, age=? where NA Me=? ", @1,@23,@" Feng Yu "];    if (result) {        NSLog (@ "Modify data successfully!");    } else{                NSLog (@ "Failed to modify data!");}    }

Delete data

Delete-(ibaction) DeleteData: (ID) Sender {    //delete the specified name of the person    BOOL result=[self.db executeupdate:@ "Delete from T_ Student where name=? ", @" Zhao three "];        Delete all//    BOOL result =[self.db executeupdate:@ "delete from T_student"];        if (result) {                NSLog (@ "Delete succeeded!");    } else{                NSLog (@ "Delete failed!");    }        }

Querying data

Query data-(ibaction) Qurey: (ID) Sender {        //query specified name information//    fmresultset *rs =[self.db executequery:@ "SELECT * from T_ Student where name like? ", @" Feng Yu "];        Query All information    fmresultset *rs=[self.db executequery:@ "select *from t_student"];    [RS Next] will query from the top down to the bottom of the return value will be no while    ([Rs next]) {                int id =[rs intforcolumn:@ "id"];        int Age=[rs intforcolumn:@ "age"];        NSString * Name =[rs stringforcolumn:@ "name"];              NSLog (@ "%d,%d,%@", id,age,name);            }            Close the database    [self.db close];}

The fmdatabase thread is not secure and we can use Fmdatabasequeue to solve threading problems

@property (nonatomic,strong) fmdatabasequeue * queue; Get the path to the sandbox    NSString * filename=[nssearchpathfordirectoriesindomains (nsdocumentdirectory, Nsuserdomainmask, YES) . Lastobject stringbyappendingpathcomponent:@ "student.db"];        Create a Database Queue instance object    self.queue =[fmdatabasequeue databasequeuewithpath:filename];        [Self.queue indatabase:^ (Fmdatabase *db) {                //CREATE database table        BOOL result=  [db executeupdate:@ "CREATE table if not exists t_student (ID integer PRIMARY key autoi ncrement, name Text,age integer) "];        if (result) {                        NSLog (@ "CREATE TABLE succeeded!");        } else{                        NSLog (@ "CREATE TABLE failed!");        }                    ];

I'm writing a change because of the repetition

[Self.queue indatabase:^ (Fmdatabase *db) {                BOOL result =[db executeupdate:@ "update t_student Set id =?, age=? Where Name=?", @1,@23,@ "Feng Yu"];        if (result) {            NSLog (@ "Modify data successfully!");        } else{                        NSLog (@ "Failed to modify data!");}            ];

If we need to deal with more than one thing and make it complete or not (as long as one thing is not done, it will not be done)

[Self.queue indatabase:^ (Fmdatabase *db) {        //Open transaction  If we need to deal with a few things and make these things complete or not complete (as long as one thing is not done, it will not be completed)        [db  begintransaction];        [DB executeupdate:@ "update t_student Set id =?, age=? Where Name=?", @1,@23,@ "Feng Yu"];        [DB executeupdate:@ "update t_student Set id =?, age=? Where Name=?", @1,@23,@ "Feng Yu"];        if (if found to be incorrect) {            //ROLLBACK TRANSACTION            [db rollback];                         [DB executeupdate:@ "update t_student Set id =?, age=? Where Name=?", @1,@23,@ "Feng Yu"];                    }                Commit TRANSACTION        [DB commit];        [DB executeupdate:@ "update t_student Set id =?, age=? Where Name=?", @1,@23,@ "Feng Yu"];}];     

IOS Data Storage FMDB