Question

如何检查列是否已有值？可以用光标找到吗？

我有两个表，一个是表info，另一个是表workDetails

表格信息：ID(PK), Name, Weather, Date, Status, TimeIn_Info, TimeOut_Info

表工作详细信息：ID(PK),Project,WorkDescription,Per,TimeIn,TimeOut // 4 row

我的WorkDetails中有4行，我只希望插入只有值的行。对于TimeOut_Info，它将来自表TimeOut中的WorkDetails。如果第4行为空，它将转到第3行。如果第3行中存在TimeOut值，它将插入表Info并且不会查找第2行和第1行....

 public void checkRow2(String a, String b, String c, String d) {
       if ((TextUtils.isEmpty(a)) && (TextUtils.isEmpty(b)) && (TextUtils.isEmpty(c)) && (TextUtils.isEmpty(d))) {
          // Toast.makeText(getApplicationContext(), "Doss", Toast.LENGTH_LONG).show();
           Toast.makeText(getApplicationContext(), "Row 2 is empty", Toast.LENGTH_LONG).show();
           return;

       }else if ((a != null && a.trim().length() > 0) && ((TextUtils.isEmpty(b)) && (c != null && c.trim().length() > 0) && (d != null && 

d.trim().length() > 0))) {
               WD.insertWorkDetails(a2, a, b, c, d);
               Cursor mCursor = database.rawQuery("SELECT TimeOut_Info FROM " + MyDatabaseHelper.TABLE_INFO + " WHERE " +
                       MyDatabaseHelper.TimeOut_Info + "= '" + d + "'", null);
 if (mCursor == null) {
               database = dbHelper.getWritableDatabase();
               ContentValues values = new ContentValues();
               values.put(MyDatabaseHelper.TimeOut_Info, d);
               database.insert(MyDatabaseHelper.TABLE_INFO, null, values);
               Toast.makeText(getApplicationContext(), "No Per2", Toast.LENGTH_LONG).show();
           }

我附加的编码else-if路径虽然已满足条件，但不起作用。我想知道检查所选列是否已有值的方法是什么？

 Cursor cur = databaseb.rawQuery("SELECT COlumn COUNT(*) FROM +MyDatabaseHelper.TABLE_INFO+ ", null);
        if (cur.getCount() > 0){
            //do nothing everything's as it should be
        }
        else{
//
}

我尝试了另一种方法，但仍然没有运气:(

Answer 1

有点难以弄清楚你要做什么，但是如果你有一个User表，由UserId键入，带有可选（可为空）UserDescription，并且您想要检查特定用户是否有描述， SQL 这样做可以是以下之一：

-- Return non-null value if user has description, null if not, or no record if user not found
SELECT UserDescription
  FROM User
 WHERE UserId = ?

-- Return 1 if user has description, 0 if not, or no record if user not found
SELECT CASE WHEN UserDescription IS NULL THEN 0 ELSE 1 END AS HasDescription
  FROM User
 WHERE UserId = ?

-- Return 1 if user has description, or no record if not or if user not found
SELECT 1
  FROM User
 WHERE UserId = ?
   AND UserDescription IS NOT NULL

-- Return 1 if user has description, or 0 if not or if user not found
SELECT COUNT(*)
  FROM User
 WHERE UserId = ?
   AND UserDescription IS NOT NULL

还有更多方法可以做到。

如何检查列是否已有值？

1 个答案: