Top "Exists" questions

Testing for the existence of a field in a class

i have a quick question. I have a 2D array that stores an instance of a class. The elements of …

python class exists

JavaScript if var exists

I want my code so that if a specific var exists it will perform an action, else it will be …

javascript if-statement exists var

Trying to delete when not exists is not working. Multiple columns in primary key

I am currently trying to delete from Table A where a corresponding record is not being used in Table B. …

sql sql-delete exists not-exists

ALTER TABLE Sqlite: how to check if a column exists before alter the table?

I need to execute in python a SQL query that adds a new column, in sqlite3. The problem is that …

python sqlite exists alter

Is EXISTS more efficient than COUNT(*)>0?

I'm using MySQL 5.1, and I have a query that's roughly of the form: select count(*) from mytable where a = "foo" …

mysql performance exists

Check if server path is available as file share in C#

I want to quickly check if a file share is available in C#, but without knowing anything about the directories …

c# .net share exists unc

Return true if all column values are true

Is there a faster way in PostgreSQL to essentially do an if on several rows? Say I have a table …

sql postgresql aggregate-functions exists boolean-logic

If Exist or Exists?

Is it possible to test two EXISTS conditions in a single IF SQL statement? I've tried the following. IF EXIST (…

sql sql-server conditional exists

What's different between Contains and Exists in List<T>?

I want to know what's different between Contains and Exists in List<T> ? They can both determine whether …

c# list contains exists

MySQL Procedure check if record exists before insert not working

I have looked at the other questions on here about this. It isn't working. DELIMITER $$ CREATE DEFINER=`root`@`localhost` PROCEDURE `…

mysql stored-procedures insert exists not-exists