Android - Check if a row within the DB exists

Question

I've created a method where the app checks if a number exists in the DB:

    Cursor player = playerDatabase.rawQuery("select * from playerTable where playerNumber ="+number,null);
  try {
      if (player.getCount() >= 0) {
          player.close();
          return true;
      }
      else{
          return false;
      }
  }finally {
      if(player != null){
          player.close();
      }
  }

But the problem is, this always returns true? The reason I am using it this way, is from the previous answers on Stack Overflow. What is the optimal way of being able to check if a search query returns a row/check if this number exits?

While I don't know the perfect answer for that, I'd in general add a limiting limit 1 to your query. That way the engine will be able to drop out after the first (potentially only possible) hit rather then iterating over all entries. This might be non-relevant if the column is set to be unique, but you never know. :) — Mario
– Mario, Commented May 13, 2018 at 21:15
This is a logical error, You said you just want to check if the number exists but you use greater or equal to zero instead just greater than zero change this if (player.getCount() >= 0) to if (player.getCount() >0) — Xenolion
– Xenolion, Commented May 13, 2018 at 21:20
Can you provide datatype definitions of DB and the code of "player.getCount()" method. — Nuwan Alawatta
– Nuwan Alawatta, Commented May 13, 2018 at 21:28
@Xenolion I did try this but it does not work if the row exists — user9784266
– user9784266, Commented May 13, 2018 at 21:30

Micheal Choudhary · Accepted Answer · 2018-05-13 22:44:54Z

1

This is the most efficient way to find if a row exists or not.

SELECT EXISTS(SELECT 1 FROM playerTable WHERE playerNumber="Here comes the player number");

It will return 1 if there is a row with playerNumber in the table or will return 0 if there is no row in the table.

answered May 13, 2018 at 22:44

Micheal Choudhary

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5 Comments

user9784266 Over a year ago

Thank you, will give this a go

Micheal Choudhary Over a year ago

@YassarHaq Give it a try and dont forget to create index on playerTable.playerNumber.

user9784266 Over a year ago

When you say create index, what do you mean? Can you possibly provide some documentation/example on this, please. Also, tried this and it looks to have worked thanks

Micheal Choudhary Over a year ago

Here is what index and how to create it . sqlitetutorial.net/sqlite-index

Micheal Choudhary Over a year ago

Dont use the random index commands without reading about them.

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