fmdb基本操作

sql常用语句

创建表

CREATE TABLE IF NOT EXISTS "T_Person" (

"id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,

"name" TEXT,

"age" INTEGER,

"heigth" REAL

)

//下边是sqllite编译器里边的语句

/*简单约束*/

CREATE TABLE IF NOT EXISTS t_student

(

id INTEGER PRIMARY KEY AUTOINCREMENT,

name TEXT,

age INTEGER

);

CREATE TABLE IF NOT EXISTS t_student

(

id INTEGER PRIMARY KEY AUTOINCREMENT,

name TEXT UNIQUE,

age INTEGER

);

/*添加主键*/

CREATE TABLE IF NOT EXISTS t_student

(

id INTEGER PRIMARY KEY AUTOINCREMENT,

name TEXT,

age INTEGER,

score REAL

);

/*添加主键*/

CREATE TABLE IF NOT EXISTS t_student

(

id INTEGER,

name TEXT,

age INTEGER,

score REAL,

PRIMARY KEY(id)

);

查询

/*分页*/

SELECT * FROM t_student

ORDER BY id ASC LIMIT 30, 10;

/*排序*/

SELECT * FROM t_student

WHERE score > 50

ORDER BY age DESC;

SELECT * FROM t_student

WHERE score < 50

ORDER BY age ASC , score DESC;

/*计量*/

SELECT COUNT(*)

FROM t_student

WHERE age > 50;

/*别名*/

SELECT name as myName, age as myAge, score as myScore

FROM t_student;

SELECT name myName, age myAge, score myScore

FROM t_student;

SELECT s.name myName, s.age myAge, s.score myScore

FROM t_student s

WHERE s.age > 50;

/*查询*/

SELECT name, age, score FROM t_student;

SELECT * FROM t_student;

修改

UPDATE t_student

SET name = 'MM'

WHERE age = 10;

UPDATE t_student

SET name = 'WW'

WHERE age is 7;

UPDATE t_student

SET name = 'XXOO'

WHERE age < 20;

UPDATE t_student

SET name = 'NNMM'

WHERE age < 50 and score > 10;

/*更新记录的name*/

UPDATE t_student SET name = 'zhangsan';

删除

DELETE FROM t_student;

DELETE FROM t_student WHERE age < 50;

插入

INSERT INTO t_student

(age, score, name)

VALUES

('28', 100, 'zhangsan');

INSERT INTO t_student

(name, age)

VALUES

('lisi', '28');

INSERT INTO t_student

(score)

VALUES

(100);

删除表

/*删除表*/

DROP TABLE IF EXISTS t_student;

FMDB

什么是FMDB

FMDB是iOS平台的SQLite数据库框架

FMDB以OC的方式封装了SQLite的C语言API

FMDB的优点

使用起来更加面向对象,省去了很多麻烦、冗余的C语言代码

对比苹果自带的Core Data框架,更加轻量级和灵活

提供了多线程安全的数据库操作方法,有效地防止数据混乱

FMDB 的github地址

https://github.com/ccgus/fmdb

FMDB有三个主要的类

FMDatabase

一个FMDatabase对象就代表一个单独的SQLite数据库

用来执行SQL语句

FMResultSet

使用FMDatabase执行查询后的结果集

FMDatabaseQueue

用于在多线程中执行多个查询或更新,它是线程安全的

通过指定SQLite数据库文件路径来创建FMDatabase对象

FMDatabase *db = [FMDatabase databaseWithPath:path];

if (![db open]) {

NSLog(@"数据库打开失败!");

}

文件路径有三种情况

具体文件路径

如果不存在会自动创建

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

在FMDB中,除查询以外的所有操作,都称为“更新”

create、drop、insert、update、delete等

使用executeUpdate:方法执行更新

- (BOOL)executeUpdate:(NSString*)sql, ...

- (BOOL)executeUpdateWithFormat:(NSString*)format, ...

- (BOOL)executeUpdate:(NSString*)sql withArgumentsInArray:(NSArray *)arguments

示例

[db executeUpdate:@"UPDATE t_student SET age = ? WHERE name = ?;", @20, @"Jack"]

查询的方法

查询方法

- (FMResultSet *)executeQuery:(NSString*)sql, ...

- (FMResultSet *)executeQueryWithFormat:(NSString*)format, ...

- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments

示例

// 查询数据

FMResultSet *rs = [db executeQuery:@"SELECT * FROM t_student"];

// 遍历结果集

while ([rs next]) {

NSString *name = [rs stringForColumn:@"name"];

int age = [rs intForColumn:@"age"];

double score = [rs doubleForColumn:@"score"];

}

FMDatabaseQueue

FMDatabase这个类是线程不安全的,如果在多个线程同时使用一个FMDatabase实例,会造成数据混乱问题

为了保证线程安全,FMDB提供方便快捷的FMDatabaseQueue类

FMDatabaseQueue 的创建

FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:path];

简单使用

[queue inDatabase:^(FMDatabase *db) {

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];

FMResultSet *rs = [db executeQuery:@"select * from t_student"];

while ([rs next]) {

// …

}

}];

使用事务

[queue inTransaction:^(FMDatabase *db, BOOL *rollback) {

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];

[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];

FMResultSet *rs = [db executeQuery:@"select * from t_student"];

while ([rs next]) {

// …

}

}];

事务回滚

*rollback = YES;

总结:本博客主要学习了sql增删改查语句,学习了FMDB的框架的三个类:

FMDatabase对象就代表一个单独的SQLite数据库,FMDatabase执行查询后的结果集,FMDatabaseQueued串行队列,同步任务;

下次学习,感觉coreDate好强大,估计你用熟悉了,你就不想用sql语句

作者:董军1990

链接:http://www.jianshu.com/p/143c83362909

來源:简书

著作权归作者所有。商业转载请联系作者获得授权,非商业转载请注明出处。

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