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FMDB总结

打开数据库

根据path打开数据库

// 1..创建数据库对象
FMDatabase *db = [FMDatabase databaseWithPath:path];
// 2.打开数据库
if ([db open]) {
    // do something
} 
else {
    NSLog(@"fail to open database");
}

文件路径有三种

• 路径不存在

  会自动创建

• 空字符串 @””

  会在临时目录创建一个空的数据库，当FMDatabase连接关闭时，数据库文件也被删除

• nil

  会创建一个内存中临时数据库，当FMDatabase连接关闭时，数据库会被销毁

数据库操作

查询

查询方法

• (FMResultSet )executeQuery:(NSString)sql
• (FMResultSet )executeQueryWithFormat:(NSString)format

// 4.查询
NSString *sql = @"select id, name, age FROM t_student";
FMResultSet *rs = [db executeQuery:sql];
while ([rs next]) {
    int id = [rs intForColumnIndex:0];
    NSString *name = [rs stringForColumnIndex:1];
    int age = [rs intForColumnIndex:2];
    Student *student = [[Student alloc] init];
    student.name = name;
    student.age = age;
    [students addObject:student];
}

更新

在FMDB中，除查询以外的所有操作，都称为“更新”

• create
• drop
• insert
• update
• delete

使用executeUpdate:执行更新

创建表

NSString *createTableSqlString = @"CREATE TABLE IF NOT EXISTS t_student (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL)";
[db executeUpdate:createTableSqlString];

写入数据

NSString *sql = @"insert into t_student (name, age) values (?, ?)";
NSString *name = [NSString stringWithFormat:@"Jack - %d",arc4random()];
NSNumber *age = [NSNumber numberWithInt:arc4random_uniform(100)];
[db executeUpdate:sql, name, age];

删除数据

// 删除数据
NSString *sql = @"delete from t_student where id = ?";
[db executeUpdate:sql, [NSNumber numberWithInt:1]];

更改数据

// 更改数据
NSString *sql = @"update t_student set name = 'Tom'  where id = ?";
[db executeUpdate:sql, [NSNumber numberWithInt:2]];

使用executeUpdateWithFormat: 执行更新

// 使用executeUpdateWithFormat: - 不确定的参数用%@，%d等来占位
NSString *sql = @"insert into t_student (name,age) values (%@,%i)";
NSString *name = [NSString stringWithFormat:@"孙悟空 - %d",arc4random()];
[db executeUpdateWithFormat:sql, name, arc4random_uniform(100)];

使用 executeUpdate:withParameterDictionary:执行更新

// 使用 executeUpdate:withParameterDictionary:
NSString *name = [NSString stringWithFormat:@"玉皇大帝 - %d",arc4random()];
NSNumber *age = [NSNumber numberWithInt:arc4random_uniform(100)];
NSDictionary *studentDict = [NSDictionary dictionaryWithObjectsAndKeys:name, @"name", age, @"age", nil];
[db executeUpdate:@"insert into t_student (name, age) values (:name, :age)" withParameterDictionary:studentDict];

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