]create table y( f int );insert into y values(1); insert into y values(3);insert into y values(2); insert into y values(4);insert into y values(5); insert into y values(6);insert into y values(7); select 'The da
SQLITE_EMPTY 16 /* Database is empty */ #define SQLITE_SCHEMA 17 /* The database schema changed */ #define SQLITE_TOOBIG 18 /* String or BLOB exceeds size limit */ #define SQLITE_CONSTRAINT 19 /* Abort due to constraint violation */ #define SQLITE_MISMATCH 20 /* Data type mismatch...
sqliteConnect --connectionString "Data Source=bdTechnologySQLiteConnect.db;Version=3;UseUTF16Encoding=True;" dbConnection=connection connectionString=connectionString dbPath=path success=success // Check whether the connection variable is empty or not. assert --message "Unable to connect to Database!"...
expr [NOT ]like-opexpr [ESCAPE expr ] | unary-opexpr | (expr) | column-name | table-name.column-name | database-name.table-name.column-name | literal-value | parameter | function-name(expr-list | * ) | expr ISNULL | expr NOTNULL | expr [NOT ] BETWEEN expr AND expr | expr ...
MySQL中字段为NULL时依然占用空间,会使索引、索引统计更加复杂。从NULL值更新到非NULL无法做到原地更新,容易发生索引分裂影响性能。尽可能将NULL值用有意义的值代替,也能避免SQL语句里面包含is not null的判断。 text类型优化 由于text字段储存大量数据,表容量会很早涨上去,影响其他字段的查询性能。建议抽取出来放在子表...
{privateUserDBHelper mHelper;//声明一个用户数据库帮助器的对象privateEditText et_name;privateEditText et_age;privateEditText et_height;privateEditText et_weight;privatebooleanisMarried =false; @OverrideprotectedvoidonCreate(Bundle savedInstanceState) ...
Database lock protocol error */ #define SQLITE_EMPTY 16 /* 数据库为空,Database is empty */ #define SQLITE_SCHEMA 17 /* 数据库结构发生改变,The database schema changed */ #define SQLITE_TOOBIG 18 /* 数据大小超限,String or BLOB exceeds size limit */ #define SQLITE_CONSTRAINT 19 /* ...
print('the [{}] is empty or equal None!'.format(sql)) def create_table(conn, sql):'''创建数据库表:student'''ifsql is not None and sql != '': cu=get_cursor(conn)ifSHOW_SQL: print('执行sql:[{}]'.format(sql)) cu.execute(sql) ...
isEmpty(name)) { Toast.makeText(this, "不能为空", Toast.LENGTH_SHORT).show(); return; } else { String phone = dao.query(name); if (phone != null) { Toast.makeText(this, "查询到的号码为:" + phone, Toast.LENGTH_SHORT).show(); } else { Toast.makeText(this, "无此联系人...
(), NULL, NULL, NULL);if(res != SQLITE_OK){QMessageBox::warning(this,"提示", "插入失败!");}//更新显示on_pushButton_Search_clicked();}void stu::on_lineEdit_InsertName_textEdited(const QString &arg1){if(arg1.isEmpty()){ui->pushButton_Insert->setEnabled(false);}else {ui->push...