SQLite check if a row exists

问题:

I'm trying to check if a specific ID exists in a table named "Products" in my sqlite database.

def existsCheck( db, id )     temp = db.execute( "select exists(         select 1         from Products         where promoID = ?     ) ", [id] ) end 

that's my current code but that returns an array which means I have to deal with conversion before I can use it as a boolean. Any ideas how I can change it so that it returns an int with the value 1?

回答1:

There is no need to use a subquery:

def existsCheck( db, id )     db.execute( "select 1                  from Products                  where promoID = ?",                 [id] ).length > 0 end 

This returns a boolean result.

回答2:

Change it to:

def existsCheck( db, id )     temp = db.execute( "select 1 where exists(         select 1         from Products         where promoID = ?     ) ", [id] ).any? end 

SQL query returns 1 when condition is met or empty result set if it's not. Whole function returns boolean depending on result set.

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