In Redis, the EXISTS
command checks whether the specified keys exist. It returns an integer reply with the number of keys that exist.
We can use the command to check for the existence of one key or multiple keys.
Syntax
The syntax goes like this:
EXISTS key [key ...]
Where key
is each key to check. This syntax indicates that we can check for as many keys as we need, simply by appending them to the previous key (with a space between).
Example
Here’s an example of using EXISTS
to check for a single key:
EXISTS pets
Result:
(integer) 1
In this case I got an integer reply of 1
, which means that the key does exist.
Here’s what happens when the key doesn’t exist:
EXISTS nonexistentkey
Result:
(integer) 0
This time we get an integer reply of 0
, which means that the key doesn’t exist.
Check Multiple Keys
As mentioned, we can check for the existence of as many keys as we like:
EXISTS pets nonexistentkey score country
Result:
(integer) 3
In this case, three of the four keys do exist and so we get an integer reply of 3
.
Duplicate Keys
Be careful not to accidentally include the same key multiple times. Including a key multiple times will result in that key being counted multiple times. So you may get misleading results if the key happens to exist.
Example:
EXISTS pets pets pets
Result:
(integer) 3