[置顶] iOS学习笔记（十六）——数据库操作(使用FMDB) .

iOS中原生的SQLite API在使用上相当不友好，在使用时，非常不便。于是，就出现了一系列将SQLite API进行封装的库，例如FMDB、PlausibleDatabase、sqlitepersistentobjects等，FMDB ( https://github.com/ccgus/fmdb ) 是一款简洁、易用的封装库，这一篇文章简单介绍下FMDB的使用。

在FMDB下载文件后，工程中必须导入如下文件，并使用 libsqlite3.dylib 依赖包。

FMDB同时兼容ARC和非ARC工程，会自动根据工程配置来调整相关的内存管理代码。

FMDB常用类：

FMDatabase ： 一个单一的SQLite数据库，用于执行SQL语句。
FMResultSet ：执行查询一个FMDatabase结果集，这个和android的Cursor类似。
FMDatabaseQueue ：在多个线程来执行查询和更新时会使用这个类。

创建数据库：

db = [FMDatabase databaseWithPath:database_path];

db = [FMDatabase databaseWithPath:database_path];

         1、当数据库文件不存在时，fmdb会自己创建一个。

         2、 如果你传入的参数是空串：@"" ，则fmdb会在临时文件目录下创建这个数据库，数据库断开连接时，数据库文件被删除。

         3、如果你传入的参数是 NULL，则它会建立一个在内存中的数据库，数据库断开连接时，数据库文件被删除。

打开数据库：

[db open]

[db open]

返回BOOL型。

关闭数据库：

[db close]

[db close]

数据库增删改等操作：

除了查询操作，FMDB数据库操作都执行executeUpdate方法，这个方法返回BOOL型。

看一下例子：

创建表：

if ([db open]) {
        NSString *sqlCreateTable =  [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS '%@' ('%@' INTEGER PRIMARY KEY AUTOINCREMENT, '%@' 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];

    }

if ([db open]) {
        NSString *sqlCreateTable =  [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS '%@' ('%@' INTEGER PRIMARY KEY AUTOINCREMENT, '%@' 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];

    }

添加数据：

if ([db open]) {
       NSString *insertSql1= [NSString stringWithFormat:
                              @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES ('%@', '%@', '%@')",
                              TABLENAME, NAME, AGE, ADDRESS, @"张三", @"13", @"济南"];
       BOOL res = [db executeUpdate:insertSql1];
       NSString *insertSql2 = [NSString stringWithFormat:
                               @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES ('%@', '%@', '%@')",
                               TABLENAME, NAME, AGE, ADDRESS, @"李四", @"12", @"济南"];
       BOOL res2 = [db executeUpdate:insertSql2];

       if (!res) {
           NSLog(@"error when insert db table");
       } else {
           NSLog(@"success to insert db table");
       }
       [db close];

   }

 if ([db open]) {
        NSString *insertSql1= [NSString stringWithFormat:
                               @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES ('%@', '%@', '%@')",
                               TABLENAME, NAME, AGE, ADDRESS, @"张三", @"13", @"济南"];
        BOOL res = [db executeUpdate:insertSql1];
        NSString *insertSql2 = [NSString stringWithFormat:
                                @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES ('%@', '%@', '%@')",
                                TABLENAME, NAME, AGE, ADDRESS, @"李四", @"12", @"济南"];
        BOOL res2 = [db executeUpdate:insertSql2];
        
        if (!res) {
            NSLog(@"error when insert db table");
        } else {
            NSLog(@"success to insert db table");
        }
        [db close];

    }

修改数据：

if ([db open]) {
        NSString *updateSql = [NSString stringWithFormat:
                               @"UPDATE '%@' SET '%@' = '%@' WHERE '%@' = '%@'",
                               TABLENAME,   AGE,  @"15" ,AGE,  @"13"];
        BOOL res = [db executeUpdate:updateSql];
        if (!res) {
            NSLog(@"error when update db table");
        } else {
            NSLog(@"success to update db table");
        }
        [db close];

    }

if ([db open]) {
        NSString *updateSql = [NSString stringWithFormat:
                               @"UPDATE '%@' SET '%@' = '%@' WHERE '%@' = '%@'",
                               TABLENAME,   AGE,  @"15" ,AGE,  @"13"];
        BOOL res = [db executeUpdate:updateSql];
        if (!res) {
            NSLog(@"error when update db table");
        } else {
            NSLog(@"success to update db table");
        }
        [db close];

    }

删除数据：

if ([db open]) {

        NSString *deleteSql = [NSString stringWithFormat:
                               @"delete from %@ where %@ = '%@'",
                               TABLENAME, NAME, @"张三"];
        BOOL res = [db executeUpdate:deleteSql];

        if (!res) {
            NSLog(@"error when delete db table");
        } else {
            NSLog(@"success to delete db table");
        }
        [db close];

    }

if ([db open]) {
        
        NSString *deleteSql = [NSString stringWithFormat:
                               @"delete from %@ where %@ = '%@'",
                               TABLENAME, NAME, @"张三"];
        BOOL res = [db executeUpdate:deleteSql];
        
        if (!res) {
            NSLog(@"error when delete db table");
        } else {
            NSLog(@"success to delete db table");
        }
        [db close];

    }

数据库查询操作：

查询操作使用了executeQuery，并涉及到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];
    }

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的FMResultSet提供了多个方法来获取不同类型的数据：

数据库多线程操作：

        如果应用中使用了多线程操作数据库，那么就需要使用FMDatabaseQueue来保证线程安全了。 应用中不可在多个线程中共同使用一个FMDatabase对象操作数据库，这样会引起数据库数据混乱。 为了多线程操作数据库安全，FMDB使用了FMDatabaseQueue，使用FMDatabaseQueue很简单，首先用一个数据库文件地址来初使化FMDatabaseQueue，然后就可以将一个闭包(block)传入inDatabase方法中。 在闭包中操作数据库，而不直接参与FMDatabase的管理。

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 < 50; ++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,@"济南"];
               if (!res) {
                   NSLog(@"error to inster data: %@", name);
               } else {
                   NSLog(@"succ to inster data: %@", name);
               }
           }];
       }
   });

   dispatch_async(q2, ^{
       for (int i = 0; i < 50; ++i) {
           [queue inDatabase:^(FMDatabase *db2) {
               NSString *insertSql2= [NSString stringWithFormat:
                                      @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES (?, ?, ?)",
                                      TABLENAME, NAME, AGE, ADDRESS];

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

               BOOL res = [db2 executeUpdate:insertSql2, name, age,@"北京"];
               if (!res) {
                   NSLog(@"error to inster data: %@", name);
               } else {
                   NSLog(@"succ to inster data: %@", name);
               }
           }];
       }
   });

 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 < 50; ++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,@"济南"];
                if (!res) {
                    NSLog(@"error to inster data: %@", name);
                } else {
                    NSLog(@"succ to inster data: %@", name);
                }
            }];
        }
    });
    
    dispatch_async(q2, ^{
        for (int i = 0; i < 50; ++i) {
            [queue inDatabase:^(FMDatabase *db2) {
                NSString *insertSql2= [NSString stringWithFormat:
                                       @"INSERT INTO '%@' ('%@', '%@', '%@') VALUES (?, ?, ?)",
                                       TABLENAME, NAME, AGE, ADDRESS];
                
                NSString * name = [NSString stringWithFormat:@"lilei %d", i];
                NSString * age = [NSString stringWithFormat:@"%d", 10+i];
                
                BOOL res = [db2 executeUpdate:insertSql2, name, age,@"北京"];
                if (!res) {
                    NSLog(@"error to inster data: %@", name);
                } else {
                    NSLog(@"succ to inster data: %@", name);
                }
            }];
        }
    });

demo下载

/**

* @author 张兴业

*  http://blog.csdn.net/xyz_lmn