sql-command ::=DROP INDEX [IF EXISTS] [database-name.] index-name DROP INDEX语句删除由CREATE INDEX语句创建的索引。索引将从数据库结构和磁盘文件中完全删除,唯一的恢复方法是重新输入相应的CREATE INDEX命令。 DROP TABLE语句在缺省模式下不减小数据库文件的大小。空间会留给后来的INSERT语句使用。要释放删除...
我们可以根据查询结果判断用户是否存在。 result=cursor.fetchone()# 获取查询结果的第一条记录ifresult:print(f"User{username_to_check}exists in the database.")# 用户存在else:print(f"User{username_to_check}does not exist in the database.")# 用户不存在 1. 2. 3. 4. 5. 8. 关闭游标和连接 ...
} else if (v == btn_deleteTable) {// 删除表 mysql.execSQL(“DROP TABLE himi”); tv.setText(“删除表成功!点击查看数据库查询”); } else if (v == btn_newTable) {// 新建表 String TABLE_NAME = “himi”; String ID = “id”; String TEXT = “text”; String str_sql2 = “CREA...
getDatabaseName(); } else { return DB_NAME; } } @Override public void onCreate(SQLiteDatabase db) { Log.d(TAG, "onCreate"); String create_sql = "CREATE TABLE IF NOT EXISTS person (" + "_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL ," + "name VARCHAR NOT NULL," + "age ...
1。与 LIKE 运算符不同的是，GLOB 是大小写敏感的，对于下面的通配符，它遵循 UNIX 的语法。
ELSE eqs.statement_end_offset END - ((eqs.statement_start_offset/2) + 1))) AS querytext, eqs.creation_time, eqs.last_execution_time, eqs.execution_count, eqs.total_worker_time, eqs.last_worker_time, eqs.min_worker_time, eqs.max_worker_time, ...
publicTask<int>SaveNoteAsync(Notenote){if(note.ID!=0){// Update an existing note.returndatabase.UpdateAsync(note);}else{// Save a new note.returndatabase.InsertAsync(note);}}publicTask<int>DeleteNoteAsync(Notenote){// Delete a note.returndatabase.DeleteAsync(note);}}}...
{ if (userDBHelper == null && version > 0) { userDBHelper = new UserDBHelper(context, version); } else if (userDBHelper == null) { userDBHelper = new UserDBHelper(context); } return userDBHelper; } //打开数据库的写连接 public SQLiteDatabase openWriteLink() { if (db == null...
if (sqlite3_exec(database, createSql, NULL, NULL, &errorMsg)==SQLITE_OK) {NSLog(@"create ok.");}else {NSLog(@"error: %s",errorMsg);sqlite3_free(errorMsg);} 1. 2. 3. 4. 5. 6. 查询结果集 结果集的查询,需要用到statement: ...
("qt_sql_default_connection"); else db = QSqlDatabase::addDatabase("QSQLITE"); //检测已连接的方式 - 自定义连接名 /*if(QSqlDatabase::contains("mysql_connection")) db = QSqlDatabase::database("mysql_connection"); else db = QSqlDatabase::addDatabase("QSQLITE","mysql_connection")...