[英]Unable to remove data from database ios
我有數據庫,但是當我嘗試從數據庫中刪除數據時,什么也沒發生,我該怎么做以確保其有效? 因為當我按下Delete時dta仍在數據庫中
這是代碼:
/file path to database
-(NSString*)filePath {
NSArray*paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"bp.sql"];
}
//open database
-(void)openDB {
if(sqlite3_open([[self filePath]UTF8String], &db) !=SQLITE_OK) {
sqlite3_close(db);
NSAssert(0, @"Databese failed to open");
}
else {
NSLog(@"database opemed");
}
}
- (IBAction)del:(id)sender {
NSString*sql = [NSString stringWithFormat:@"DELETE key, theDate, customer, code1, code2 FROM summary WHERE key=\"%@\"",customerName];
const char* query_stmt = [sql UTF8String];
sqlite3_stmt*statement;
sqlite3_prepare_v2(db, query_stmt, -1, & statement, NULL);
if (sqlite3_step(statement) == SQLITE_DONE)
{
NSAssert(0, @"database object delete failed");
} else {
NSLog(@"No error");
}
sqlite3_finalize(statement);
sqlite3_close(db)
您不能使用DELETE
查詢刪除特定的列值。 用於刪除整行。
問題在於以下查詢:
NSString*sql = [NSString stringWithFormat:@"DELETE key, theDate, customer, code1, code2 FROM summary WHERE key=\"%@\"",customerName];
更改為:
NSString*sql = [NSString stringWithFormat:@"DELETE FROM summary WHERE key=\"%@\"",customerName];
如果需要刪除行的特定列值,請使用UPDATE
查詢。
請查看sqlite文檔以獲取詳細信息
您編寫的所有函數(如檢查文件路徑,opendb)都應在同一函數中發生(可能在del函數內部)。
這就是我要做的:
-(void)updateStatus:(NSString *)queryString {
NSString *docsDir;
NSArray *dirPaths;
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
strDatabasePath = [NSString stringWithString:[docsDir stringByAppendingPathComponent:@"bp.sql"]];
NSFileManager *filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath: strDatabasePath] == YES)
{
const char *dbpath = [strDatabasePath UTF8String];
if (sqlite3_open(dbpath, &sqlDatabase) == SQLITE_OK)
{
const char* beginString = "BEGIN;";
sqlite3_stmt *compiledstatement;
sqlite3_prepare_v2(sqlDatabase, beginString, -1, &compiledstatement, NULL);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else DLog(@"Failed!");
sqlite3_finalize(compiledstatement);
DLog(@"QUERY : %@",queryString);
const char *selectStatement = [queryString UTF8String];
sqlite3_prepare_v2(sqlDatabase, selectStatement, -1, &compiledstatement, NULL);
//sqlite3_bind_text(compiledstatement,1,[statusString UTF8String],-1,SQLITE_TRANSIENT);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else DLog(@"Failed!");
sqlite3_finalize(compiledstatement);
const char* endString="END;";
sqlite3_prepare_v2(sqlDatabase, endString, -1, &compiledstatement, NULL);
if (sqlite3_step(compiledstatement) == SQLITE_DONE) {}
else DLog(@"Failed!");
sqlite3_finalize(compiledstatement);
sqlite3_close(sqlDatabase);
}
else DLog(@"Failed to open table");
}
}
NSString *queryString;
queryString = [NSString stringWithFormat:@"DELETE key, theDate, customer, code1, code2 FROM summary WHERE key=\"%@\"",customerName];
[self updateStatus:queryString];
希望這可以幫助...
-(BOOL)DeleteWishList:(int)rowno
{
NSString *queryString=[NSString stringWithFormat:@"delete from wishtable where _id=%d",rowno];
[self openDB];
char *err;
if (sqlite3_exec(dBObject, [queryString UTF8String], NULL,NULL, &err)!= SQLITE_OK)
{
sqlite3_close(dBObject);
return NO;
}
else
{
return YES;
}
}
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