数据库

数据库：

// 创建一个sqlite3对象 以后都操作它
static sqlite3 *db = nil;

#pragma mark   1. 打开数据库
- (void)openDB {
if (db == nil) {
NSString *tempPath = NSTemporaryDirectory();
NSLog(@"%@", tempPath);
NSString *filePath = [tempPath stringByAppendingPathComponent:@"student.sqlite"];

// 打开路径下的数据库
int result = sqlite3_open(filePath.UTF8String, &db);
if (result == SQLITE_OK) {
NSLog(@"打开数据库成功");
// 写sql语句(可用某些工具生成SQL语句)
NSString *sql = @"CREATE  TABLE  IF NOT EXISTS student (number INTEGER PRIMARY KEY  NOT NULL , name TEXT, age INTEGER)";
// 执行SQL语句
int result2 = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);
if (result2 == SQLITE_OK) {
NSLog(@"创建表格成功");
}else
NSLog(@"创建表格失败");

}else
NSLog(@"打开数据库失败");
}
}

#pragma mark   2. 关闭数据库
- (void)closeDB {
if (db != nil) {
int result = sqlite3_close(db);
if (result == SQLITE_OK) {
NSLog(@"关闭数据库成功");
// 同时把数据库对象置空
db = nil;
}else
NSLog(@"关闭数据库失败");
}
}

#pragma mark   3. 添加数据
- (void)insertStudent:(Student *)stu {
// 添加的sql语句
NSString *sql = [NSString stringWithFormat:@"INSERT INTO student (number, name, age) VALUES ('%@', '%@', '%d')", stu.number, stu.name, stu.age];

int result = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);
if (result == SQLITE_OK) {
NSLog(@"添加数据成功");
}else
NSLog(@"添加数据失败");
}
#pragma mark   4. 删除数据
- (void)deleteStudent:(NSString *)num {
NSString *sql = [NSString stringWithFormat:@"DELETE FROM student WHERE number = '%@'", num];
int result = sqlite3_exec(db, sql.UTF8String, NULL, NULL, NULL);
if (result == SQLITE_OK) {
NSLog(@"删除数据成功");
}else
NSLog(@"删除数据失败");
}
#pragma mark   5. 更新数据
- (void)updateStudent:(Student *)stu {
NSString *sql = [NSString stringWithFormat:@"UPDATE student SET name = '%@' , age = '%d' WHERE number = '%@'", stu.name, stu.age, stu.number];
int result = sqlite3_exec(db, sql.UTF8String, nil, nil, nil);
if (result == SQLITE_OK) {
NSLog(@"更新数据成功");
}else
NSLog(@"更新数据失败");

}

#pragma mark   6. 查询数据
- (NSMutableArray *)selectStudent {
NSMutableArray *arrayAll = [NSMutableArray array];

// 有条件的查询 直接加一个where语句就可以啦
NSString *sql = [NSString stringWithFormat:@"SELECT * FROM student"];

// 游标
sqlite3_stmt *stmt = nil;
// int nByte为-1时：自动计算sql语句的长度
int result = sqlite3_prepare_v2(db, sql.UTF8String, -1, &stmt, NULL);
if (result == SQLITE_OK) {
NSLog(@"开始查找数据");
// 一行一行的去查找数据  直到找完
while (sqlite3_step(stmt) == SQLITE_ROW) {
// 获取number
const char *num1 = (const char *)sqlite3_column_text(stmt, 0);// 第二个参数递增
NSString *number = [NSString stringWithCString:num1 encoding:NSUTF8StringEncoding];
// 获取name
const char *name1 = (const char *)sqlite3_column_text(stmt, 1);
NSString *name = [NSString stringWithCString:name1 encoding:NSUTF8StringEncoding];
// 获取age
int age = sqlite3_column_int(stmt, 2);
// 把取到的数据放到数据模型中
Student *stu = [[Student alloc] init];
stu.name = name;
stu.number = number;
stu.age = age;

[arrayAll addObject:stu];
}
}else
NSLog(@"查询失败");
// 游标用完之后要释放：
sqlite3_finalize(stmt);
return arrayAll;
}