在PDA中设计数据库后，避免不了的会根据实际的需求改动功能。最害怕的是，PAD都发下去了，很多台，而工作已经开展了，数据已经有一部分了，中间要增加功能，增加表或者增加字段，怎么办？只有在更新程序的时候，判断表是否存在，不存在则临时创建，字段也类似。
Sqlite中判断表是否存在，表名'attPointSampleEx'：
string sql = "SELECT COUNT(*) as CNT FROM sqlite_master where type='table' and name='attPointSampleEx'";
string sql1 = "CREATE TABLE [attPointSampleEx] ([ID] VARCHAR(50) NOT NULL UNIQUE,[PickName] VARCHAR(20)," +
"[SpecimenCode] VARCHAR(200), " +
"[PickTime] VARCHAR(19)," +
"[PickAddre] VARCHAR(200)," +
"[Lon] VARCHAR(20)," +
"[ZYName] VARCHAR(200), " +
"[ZYCode] VARCHAR(10), " +
"[PlantXue] VARCHAR(200), " +
"[HerbalPart] VARCHAR(50), " +
"[YongTu] VARCHAR(50), " +
"[SampleType] VARCHAR(2)," +
"[LiYong] VARCHAR(200)," +
"[WeiXie] VARCHAR(200)," +
"[Notion] VARCHAR(200));";
//_IsCreate Bool类型，判断是否创建了表
if (!_IsCreate)
{
//读取系统表，看是否有此表的记录
DataTable tDT = MainDataBase.pMainDataBase.pDataBase.getDataTableFromSql(sql);
if (tDT != null && tDT.Rows.Count>0)
{
//判断记录
_IsCreate = Convert.ToInt32(tDT.Rows[0][0]) == 1;
if (!_IsCreate)
{
//如果没有记录，则创建表
_IsCreate = MainDataBase.pMainDataBase.pDataBase.ExecuteNonQuery(sql1) >= 0;
}
tDT.Dispose();
}
}