SQlite入门

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

@interface ViewController : UIViewController
{
    sqlite3 *contactDB;
    
    UITextField *name;
    UITextField *address;
    UITextField *phone;
    
    UILabel *status;    
    
    NSString *databasePath;
}

一 创建数据库

/*根据路径创建数据库并创建一个表contact(id nametext addresstext phonetext)*/
    
    NSString *docsDir;
    NSArray *dirPaths;
    
    // Get the documents directory
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
    
    docsDir = [dirPaths objectAtIndex:0];
    
    // Build the path to the database file
    databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent: @"contacts.db"]];

    NSFileManager *filemgr = [NSFileManager defaultManager];
    
    if ([filemgr fileExistsAtPath:databasePath] == NO) 
    {
        const char *dbpath = [databasePath UTF8String];
        if (sqlite3_open(dbpath,&contactDB)==SQLITE_OK) 
        {
            char *errMsg;
            const char *sql_stmt = "CREATE TABLE IF NOT EXISTS CONTACTS(ID INTEGER PRIMARY KEY AUTOINCREMENT,NAME TEXT,ADDRESS TEXT,PHONE TEXT)";
            if (sqlite3_exec(contactDB,sql_stmt,NULL,&errMsg)!=SQLITE_OK) {
                status.text = @"创建表失败n";
            }
        }
        else 
        {
            status.text = @"创建/打开数据库失败";
        }
    }

二 增

- (IBAction)SaveToDataBase:(id)sender 
{
    sqlite3_stmt *statement;
    
    const char *dbpath = [databasePath UTF8String];
    
    if (sqlite3_open(dbpath,&contactDB)==SQLITE_OK) {
        NSString *insertSQL = [NSString stringWithFormat:@"INSERT INTO CONTACTS (name,address,phone) VALUES("%@","%@","%@")",name.text,address.text,phone.text];
        const char *insert_stmt = [insertSQL UTF8String];
        sqlite3_prepare_v2(contactDB,insert_stmt,-1,&statement,NULL);
        if (sqlite3_step(statement)==SQLITE_DONE) {
            status.text = @"已存储到数据库";
            name.text = @"";
            address.text = @"";
            phone.text = @"";
        }
        else
        {
            status.text = @"保存失败";
        }
        sqlite3_finalize(statement);
        sqlite3_close(contactDB);
    }
}

三 查

- (IBAction)SearchFromDataBase:(id)sender 
{
    const char *dbpath = [databasePath UTF8String];
    sqlite3_stmt *statement;
    
    if (sqlite3_open(dbpath,&contactDB) == SQLITE_OK) 
    {
        NSString *querySQL = [NSString stringWithFormat:@"SELECT address,phone from contacts where name="%@"",name.text];
        const char *query_stmt = [querySQL UTF8String];
        if (sqlite3_prepare_v2(contactDB,query_stmt,NULL) == SQLITE_OK) 
        {
            if (sqlite3_step(statement) == SQLITE_ROW) 
            {
                NSString *addressField = [[NSString alloc] initWithUTF8String:(const char *)sqlite3_column_text(statement,0)];
                address.text = addressField;
                
                NSString *phoneField = [[NSString alloc] initWithUTF8String:(const char *)sqlite3_column_text(statement,1    )];
                phone.text = phoneField;
                
                status.text = @"已查到结果";
                [addressField release];
                [phoneField release];
            }
            else {
                status.text = @"未查到结果";
                address.text = @"";
                phone.text = @"";
            }
            sqlite3_finalize(statement);
        }
        
        sqlite3_close(contactDB);
    }
}

（编辑：李大同）

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