面试题：Objective-C中如何在SQLite数据库中创建一张简单表

Question

请用Objective-C代码展示如何使用SQLite数据库的直接操作函数，创建一张名为'users'的表，该表包含'id'（整数类型，主键自增长），'name'（字符串类型，长度不超过50），'age'（整数类型）这三个字段。

Answer 1

#import <sqlite3.h>
#import <Foundation/Foundation.h>

- (void)createUsersTable {
    sqlite3 *database;
    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"test.db"];
    
    if (sqlite3_open([path UTF8String], &database) == SQLITE_OK) {
        const char *createTableSQL = "CREATE TABLE IF NOT EXISTS users ("
                                     "id INTEGER PRIMARY KEY AUTOINCREMENT,"
                                     "name TEXT(50),"
                                     "age INTEGER"
                                     ")";
        char *errorMessage;
        if (sqlite3_exec(database, createTableSQL, NULL, NULL, &errorMessage) != SQLITE_OK) {
            NSLog(@"创建表失败: %s", errorMessage);
            sqlite3_free(errorMessage);
        } else {
            NSLog(@"表创建成功");
        }
        sqlite3_close(database);
    } else {
        NSLog(@"无法打开数据库");
    }
}